When in Styles screen, select USER on the left side, press File > Copy, then select styles, you want to copy, press again Copy, then select destination - USB1 on the left side - and press Copy here.
The same way is for registrations, songs, multipads and playlists
As for voices, you cannot copy sound files (samples), which are stored in dedicated part of memory. You can copy only „directions“ how to process those samples, which are stored as .vce files.