If the drum moves back and forth then it needs the brake shoes to be backed off using the star wheel adjuster.
If it doesn't move you'll want to try a 3lb hammer, and be very carefull that you don't hit those studs. Hit the drum to break it free.
However if this doesn't work you'll need an oxy aceteleen tourch set. Heat the metel around the studs until it just turns red hot then take a coffee break. The expansion then contraction usually pops the drums right off.