take a nail or thin wire and push the plastic rivite's in the center where the snap pin use to be hard !! and it should push the center of the pin back inward from the inside > if you lay on your side you might be able to feel the back's of the bumper where they pushed threw > you can then squize them out by pushing them threw the bumper it won't hurt your bumper but it will show the hole's where they were mounted > hope this helps >
FYI > i just put my plate mount back on the front of my cobra > I hated the way the plate looked in it with out the mount .