This tutorial only works on windows :

  1. Press Windows+R button on keyboard 
  2. Run dialog will pop up 
  3. Type cmd and hit Enter
  4. And command prompt will open
  5. Then type attrib -h -r -s /s /d g:\*.*
    Note : Replace the letter g with your pen drive letter. 
That's all now open your pen drive and you will see the files there.