Back off the 4 nuts on the backside of the brake backing plate that hold the bearing retainer plate. With the nuts at the end of the studs, tap them toward the outside. This should move the retainer plate. IF not, just gently pry it loose from the backing plate.
Then you may need an axle puller, or you can try putting the brake drum on backwards with a few lug nuts and use the drum like a slide hammer to pull the axle out.