There might be some hidden files when accessing USB sticks. There are 2 choices: Configure the file explorer to see hidden files, or make the files visible by modifying their attributes.
You can see them by setting the file explorer’s
Folder Option > View > Advanced Settings > Files and Folders by unchecking the followings:
Hide extension for known file types
Hide protected operating system files (Recommended)
Hidden files and folders > Show hidden files, folders, and drives
You can use the command prompt to remove all hidden or system attributes within the current folder:
attrib -H -S /D *