Only copying the DB file will not copy all the external metadata, like video preview pictures, loudness analysis, intro detections, manually added posters and the like.
If you want to do it right, copy the whole Plex data folder.
While doing the copy, the source and the destination Plex server must be not running. If they do, you’ll end up with a destroyed main database file.
You must make sure that the external drive with your media is getting the exact same drive letter on both Windows machines. https://www.howtogeek.com/96298/assign-a-static-drive-letter-to-a-usb-drive-in-windows-7/
