Welcome to the board
Can't see the photo but I would assume you mean wear patches? Heat gun should take them right off. Might take a little time to heat the glue properly, which means hot, as in too hot to touch. If it is an older boat, where the patches were will probably show no matter how much time you spend attempting to clean it up with Acetone. Might be better to grind it some, and mount the bimini mounting plates to the top of the wear patch. Will make a solid footing for the bimini to mount too.