É exatamente o que estou fazendo Davi.

Utilizei a opção Import/Export na ZMI e Exportei o arquivo CORE.zexp. Aproveitei e copiei também o arquivo Data.fs na versão 2.1.2.

Depois instalei o 3.1.1 e com a mesma opção importei o arquivo CORE.zexp. A seguinte mensagem de erro foi exibida:

"Site Error
An error was encountered while publishing this resource.

Error Type: BadRequest
Error Value: The id "CORE" is invalid - it is already in use.

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Troubleshooting Suggestions

The URL may be incorrect.
The parameters passed to this resource may be incorrect.
A resource that this resource relies on may be encountering an error.
For more detailed information about the error, please refer to the error log.

If the error persists please contact the site maintainer. Thank you for your patience."

Depois copiei o arquivo Data.fs para o caminho C:\Arquivos de programas\Plone 3\Data\var, fechei o plone e abri novamente.

Consegui entrar na ZMI e identifiquei os itens do plone site anterior, mas quando tentei executar a página, recebi a seguinte mensagem de erro:

"Site Error
An error was encountered while publishing this resource.

ComponentLookupError

(, 'plone.leftcolumn') (Also, the following error occurred while attempting to render the standard error message, please see the event log for full details: (<InterfaceClass plone.app.viewletmanager.interfaces.IViewletSettingsStorage>, ''))Traceback (innermost last): Module ZPublisher.Publish, line 202, in publish_module_standard Module ZPublisher.Publish, line 150, in publish Module plone.app.linkintegrity.monkey, line 21, in zpublisher_exception_hook_wrapper Module Zope2.App.startup, line 221, in zpublisher_exception_hook Module ZPublisher.Publish, line 119, in publish Module ZPublisher.mapply, line 88, in mapply Module ZPublisher.Publish, line 42, in call_object Module Shared.DC.Scripts.Bindings, line 313, in __call__ Module Shared.DC.Scripts.Bindings, line 350, in _bindAndExec Module Products.CMFCore.FSPageTemplate, line 216, in _exec Module Products.CMFCore.FSPageTemplate, line 155, in pt_render Module Products.PageTemplates.PageTemplate, line 89, in pt_render Module zope.pagetemplate.pagetemplate, line 117, in pt_render Module zope.tal.talinterpreter, line 271, in __call__ Module zope.tal.talinterpreter, line 346, in interpret Module zope.tal.talinterpreter, line 891, in do_useMacro Module zope.tal.talinterpreter, line 346, in interpret Module zope.tal.talinterpreter, line 536, in do_optTag_tal Module zope.tal.talinterpreter, line 521, in do_optTag Module zope.tal.talinterpreter, line 516, in no_tag Module zope.tal.talinterpreter, line 346, in interpret Module zope.tal.talinterpreter, line 891, in do_useMacro Module zope.tal.talinterpreter, line 346, in interpret Module zope.tal.talinterpreter, line 586, in do_setLocal_tal Module zope.tales.tales, line 696, in evaluate - URL: file:C:\Arquivos de programas\Plone 3\Data\Products\CMFPlone\skins\plone_templates\global_defines.pt - Line 8, Column 0 - Expression: - Names: {'container': , 'context': , 'default':, 'here': , 'loop': {}, 'nothing': None, 'options': {'args': ()}, 'repeat': , 'request': , 'root': , 'template': , 'traverse_subpath': [], 'user': } Module zope.tales.expressions, line 217, in __call__ Module Products.PageTemplates.Expressions, line 161, in _eval Module Products.PageTemplates.Expressions, line 123, in render Module Products.CMFPlone.browser.ploneview, line 68, in globalize Module Products.CMFPlone.browser.ploneview, line 133, in _initializeData Module Products.CMFPlone.browser.ploneview, line 515, in have_portlets Module zope.component._api, line 207, in getUtility ComponentLookupError: (see above)
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Troubleshooting Suggestions

The URL may be incorrect.
The parameters passed to this resource may be incorrect.
A resource that this resource relies on may be encountering an error.
For more detailed information about the error, please refer to the error log.

If the error persists please contact the site maintainer. Thank you for your patience."

Quando executo o Plone e clico no botão View Plone ele só abri essa página:

Welcome to Zope, a high-performance object-oriented platform for building dynamic Web applications. Here are some quick pointers to get you started:

• Read The Fine Manual. This document guides you through the whole process of learning Zope, from logging in for the first time to creating your own web applications.

• Import and then check out the new example Zope applications. These examples show you simple working Zope applications that you can copy and modify.

• Go to the main Documentation Overview on Zope.org. Here you will find pointers to official and community contributed documentation.

• Look at the various Mailing Lists about Zope. The Mailing Lists are where you can get quick, accurate, friendly help from a large community of Zope users from around the world.

• Browse and search the integrated, Online Help System which contains documentation on the various kinds of components you'll find in Zope.

• Go directly to the Zope Management Interface if you'd like to start working with Zope right away. NOTE: Some versions of Microsoft Internet Explorer, (specifically IE 5.01 and early versions of IE 5.5) may have problems displaying Zope management pages. If you cannot view the management pages, try upgrading your IE installation to the latest release version, or use a different browser.

• Find out about Zope Corporation, the publishers of Zope.

Estou errando em aguma coisa? Algo pode ser corrigido baseado nas mensgens de erro mostradas? Ou é incompatibilidade de versão mesmo e só um expert pode resolver?

PS: desculpem se a mensagem foi muito extensa.