Gift: Route 8
You won't find Archen in the wild in this game — you get it as a gift.
Looking for Archeops? It isn't found in the wild in this game — evolve Archen (Level 37).
For the look, the best colour match is Great Ball, Quick Ball or Lure Ball.
Evolution: Archen → Archeops (Level 37).
Archen in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)