exportar playlist de un usb a nuevo rekordbox

Unfortunately that is not possible at this time - the best you could do would be to transfer the music from your USB drive back into your computer, then add it to your collection, and manually rebuild the playlists based on what you can see on the USB drive. With the USB drive connected to rekordbox, you can see the playlists, so you can them manually re-create them within rekordbox from the tracks you have imported.