get drive to be recognized (but don't open any files on it) open terminal and get into REPL (if possible)
>>> import storage
>>> storage.erase_filesystem()
If you can't access the REPL is to double-click the reset button and have the SAM32 mount into bootloader mode, then drag the file below onto the drive. It will restart once the transfer is complete.
Make sure to add all the default files back once you've wiped the memory!