Do you have access to another PC/Laptop (a nearby friend perhaps?) to see if their OS can 'see' the USB sticks? If they can access the stick(s) then maybe they can be fixed on their machine using the command window chkdsk /f (drive letter): command. If this can be done on their machine then formatting can also be tried. It may not fix your machine but it may fix your USB sticks as a first step.
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