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NickyNite444 - its very simple, you've probably been over thinking it.
- close calibre
- with file manager copy the library folder (I'll assume its called Calibre Library) to the thumb drive (give it a different name - e.g. MyLibrary)
- start calibre
- select Switch /Create library from library-icon dropdown menu
- locate MyLibrary on the thumb drive
- select the Use the previously existing library at the new location radio button
- click OK - calibre will switch to MyLibrary - i.e. make it the current library
- select Remove library->Calibre Library from library-icon dropdown menu. That will remove that library from calibre's configuration data, but it will not delete it from the Surface's 'disk drive', you'll need to do that with your file manager.
Moderator Notice
I'll also move this to the Library Management forum as it's not a reading device issue
BR