How do I unhide my folders?

Even if I go to the folder properties, it does not allow me to tick the attributes for hidden. Is this a virus or something? I already scanned my computer and everytime I insert my flash drive, it finds a virus. Does this mean the computer's not cleaned and the virus is in my computer's memory? I formatted my flash drive three times already and my folders in the flash drive keep on "hiding: without me being able to unhide them,