Because mimikyu are rare pokémon native only to a very specific island in Alola, this might actually be easier than you think, anonymous. Unless you live on Ula’ula Island, all you need to do is inform whoever is raising those mimikyu that as much as you love pokémon, you don’t feel comfortable around them. If you do live on Ula’ula Island, rest assured that mimikyu detest sunlight, and for that reason, they only make their home in one specific spot. The likelihood of you being bothered by mimikyu, even if you live on the correct island, is actually rather low.
If, for some reason, you are suffering through an infestation of feral mimikyu, you may wish to consider contacting your local pokémon center. They should be able to dispatch trainers to your location to collect the mimikyu for rehoming or training. If you can’t reach your local pokémon center or if you live in an area without one, you may also consider acquiring a volcarona or other pokémon capable of using Sunny Day to deter the feral mimikyu from getting too close to your property.