remove corrupted linux install from external hdd

Hi all, looking to see if someone can point me in the right direction.  I had an external hdd which I'd previously only used for storage.  I was messing around learning some linux and tried installing it on the external hdd, it worked, then i tried to take it off.  now i can't access anything on the drive.

hoping someone can point me in the right direction, perhaps with external tools i might be able to use to recover my files, at least

thanks in advance