This is so sad. I commend you, OP, for trying to help. But like others have suggested, I really hope you can convince your mother to re-home the pets.

Imagine if you had to live in this room. What a horrible, miserable existence. Most humans would attempt suicide after living in this room for long enough. This is cruelty, and even if you clean it, don’t you think it’s just going to happen again? The animals deserve more than a laundry room. Even if it were clean this would be cruel.

Maybe you can convince her to let them go. Once you’ve cleaned it try asking her if she wouldn’t like to maintain that clean laundry room. You could offer to re-home the pets for her and then give the room a renovation with some new shelving, etc. to turn it into a useless area for her. Maybe she can get excited about having a new, clean space. And the pets will be able to have a happy, healthy life somewhere else.