Looks like the files got placed into hidden mode.
Click on Start, and open the Start Menu.
In the Start Menu search box area type cmd and press Enter.
Let's say your flash drive or SD card is e:
At the command prompt, copy/paste the following:
attrib -h -r -s /s /d e:\*.*
(Replace the letter e with your flash drive letter)
Let us know if it worked.
Retired - Doin' Dis, Dat, and slapping malware.