The following error occurred during migration: "Blocked file not migrated to SharePoint"
By default a SharePoint blocks certain file types from being uploaded by users.
You can check what file types are blocked in Central Administration - Security - Define blocked file types (SharePoint 2010)
Refer to the following article for more details:
Delete the blocked file extensions from the list of blocked files.
Verify that the global settings are not conflicting with any size limits changes in the SharePoint UI. From the tools - options menu go to the SharePoint tab and click on "blocked files". From here replace the default 50 in the top box with a higher number or set it to 0 to completely ensure there is no restriction.