Offizieller Kommentar
@Adam > Unfortunately @Norbert's instructions are for BACKUP purposes only, not to move your collection.
My recommendation is to move your entire music folder to an EMPTY external drive, then within rekordbox, select ALL your collection and use the relocate tool to point the entries to the new location. If all songs have moved the same way (eg. you only moved ONE folder with all sub-folders and files to the new location), it will relocate everything in one simple action.
After that, you have the option of also moving the database to the external drive, but that's not necessary as it doesn't take up an inordinate amount of space.