@brco_84 have you tried the "Eradicate" option on the mouse hole? I'm not sure if I've tried it, I dread to think what happens lol. I did try the landlord recently but he did nothing although they were running around him. There are mods for it apparently if you're on PC and I think the "destroy object" cheat might work too if you've used that before. I'm on console so can't use either option unfortunately. I can use the move objects cheat though so with that I placed something over the hole. I don't know if that worked permanently because I switched households shortly afterwards.
@LadyAofPineapple the mouse trap is an option by clicking on the mouse hole in the wall...poor little things 😭.
Living in the countryside we get field mice sometimes but having cats in real life has helped keep them away before (one managed to trap one under a plant pot once until I saved it). But Sims cats do nothing in my experience although I think they probably should! There's an open bug report for that issue.