help, rear brake

Hello gyus,
I have 89 Aerostar ext and I need to change pads for rear brake, drum. And guy on Autozone ask me size 3 1/2" by 9"  or 1 1/4" by 10" if I remmember right, and I try to remove thr drum by t woun't come out, it seems lose but won't come out, I need to take size on pads.
You guys have any idea how to take the drum out?
 
Thanks pros

The shoes have probably worn a lip into the drum.  You will need to pop out the little rubber oval plug on the back side of the backing plate.  Then you will need 2 small flat tip screw drives to back off the brake adjusters.  This will back the shoes off past the lip so that the drum will come off.