How to thoroughly remove mold from a fridge?

Baking soda is the approved product for fridge cleaning. It sanitizes to some extent, removes mold, and does no harm to the finish. When you have replaced all the shelves and not-rotten food, leave the open box of soda in the fridge. Plastics absorb smells; it may be a while before your fridge loses the odor.

Take everything out and spray all surfaces down with a solution of bleach and water. Clean thoroughly.

If there's a grill or other little panel on the front of the very bottom of the fridge (below the door, on the outside of the fridge, not inside the chilled part), see if you can remove it. There's often a drip tray in there that you can slide out. Moldy water can collect in it.

at the back of a fridge there's often a small drain - in my UK fridge, this is located on a ridge just above the vegetable drawers - and that can often be a lurking point for ~stuff~ - I tend to clean mine with a chopstick wrapped in a j-cloth or similar. You'll also want to take all the shelves etc. out and give it a through clean - you mentioned you've given it a cursory wipedown but in that sort of situation, the only way to get rid is to do a fullscale clean. I am a bicarb paste and vinegar girl, esp where food storage is involved but up to you, I'd dilute any bleach if you go that way. A small bowl of bicarb left in the fridge after cleaning should also help with the odour.

Also, check out the rubber door gasket/seal thoroughly: it has convolutions and folds the make it seal well, but are also breeding grounds for all sorts of nastiness.

No bleach! No bleach in your fridge! Bleach is corrosive. And gross. try doing other things first. It may just be the odor remaining at this point. Even if there is still mold, Baking soda, borax, vinegar are what I would suggest at this point. And yes, check the drain and the gaskets.

Is this a mini-fridge? Some models of refrigerator have crevices or portions under the plastic where condensation-ice may have formed = water may have deposited during the power outages. It happens in mini-fridges on occasion. I used to have a fridge with a manual that had diagrams of the whole assembly... so you could tell there was a frame spacing under the body where possibly some condensation could occur, etc... but I kind of doubt that may be available on a modern day fridge... Would it possible to take it outside and set in the sun for several days (unless outside is too humid...)? It really needs to be dried out completely before reusing.

We picked up a secondary fridge used a few years back. It has a slight moldy/musy odor that repeated cleanings did not get rid of. I eventually let it sit open in the yard for about two weeks. The sun's UV rays did the trick.

The freezer floor was a screwed down shelf in my old fridge. Check under there. Activated charcoal for the smell. If anyone recommends coffee grounds for the smell, don't do that. You will then associate coffee smell with mold smell for years.