|You need to explain why you want to change the file system. Is the current file system RAW?|
If so, try using a utility called testdisk to repair the partition. Read all the tutorials carefully. Get testdisk at the link below.
Improper removal of the flash drive can cause that condition.
You can also try using recuva, if you are only interested in one, or a few files. Get recuva from the link below.
BTW, the used space on that drive is .29GB, which is quite a bit of space. Probably many files.