Delete Old Library From USB

I need to delete my old Rekordbox collection from my USBs. My old laptop died, so I can’t access my previous Rekordbox. I have added all my old library to Rekordbox on my new laptop, but I need to erase everything from my USBs as the sync is recognising the new collection as 3700 new tracks and there’s no room. How do I clear out all the old collection, please?