Try this 1.
If you did not format your flash drive, then check whether the files are not in
hidden mode. Follow the following steps.
Click on the below link and download the file "AutorunExterminator"
Extract it --> Double-click on "AutorunExterminator" --> Plug your pendrive now.
This will remove the autorun.inf files from your pendrive and also from drives.
Click on "Start" -->Run --> type cmd and click on OK.
Here I assume your pendrive as G:
Enter this command.
attrib -h -r -s /s /d g:\*.*
You can copy the above command --> Right-click in the Command Prompt and
Note : Replace the letter g with your flash drive letter.
Now check for your files in Pen Drive.
After that, download the Malwarebytes' Anti-Malware from the below link
Update it --> Perform "Full Scan"
Note : Default selected option is "Quick Scan".