The error message "Telerik.CMS.CmsManager" does not contain a constructor that takes 1 arguments occurs because you are using Sitefinity 3.7 version prior to SP3. Please see the suggestions Ivan Dimitrov gave in his reply above.
As for the missing MigrationImportModule folder - my initial intent was to simply rename "MigrationImportModule" to "Sitefinity 4.0" but due to some problems when renaming folders in svn I created a new folder and deleted the old one. My idea is that when Sitefinity 4.1, 4.2 etc. are released with additional modules and features, we could create an extended migration modules that are specifically for versions 4.1, 4.2, etc. and that's why since the current module that imports the content targets version 4.0 there is a folder with this name.
I hope this answers your question.
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