thread size to remove drum

i'm looking for a bolt to take off the rear drum.what size/thread do i need.thanks

easiest way to take it off is buy a can of brake cleaner and spray it on the openings between the backing plate and drum then hit the drum with a hammer and it will break loose. or you could use two 8mmx1.5 bolts screw them in to the drum and it will begin to push the drum out