Solid axles such as a real axle do not use axle nuts. There will be 4 nuts, 2 on either side of the axle, on the back side of the brake drum that hold the axle in place. You’ll have to completely remove the drum brake system before removing it and will also need to remove the snap rings holding the axle inside the differential. (Requiring you to drain and refill the rear differential gear oil) you’ll also need to cut the old bearing off once the axle is removed, you won’t be able to press it off. Then you’ll need a hydraulic press to install the new bearing.

Might be worth taking it to a shop if that’s more than you wanted to sign up for.