USB flash memory has data but doesn't show the contents

Hi all, My friend's USB flash memory has data (its drive shows that there is data in it) but when I double click on it to open it and see the contents, it doesn't show any folders and files! I did the following works: 1- I scanned it by my updated kaspersky AV. but no threat found 2- Scanned by windows defender tool. same result! 3- scanned by malwarebytes anti-malware. same. 4- cmd (run...