Give the location, and how to find it. (for example, give directions to where it is on the location, or if Stoutland Search, say so.)
It doesn't exist. There is no Mimikium Z in SM, it only exists in USUM.
The Mimikium Z (Japanese: ミミッキュＺ Mimikkyu Z) is a type of Z-Crystal introduced in Pokémon Ultra Sun and Ultra Moon.
Source
Hope I helped!
