SOS Encounter: Wela Volcano Park (15%)
Looking for Magmortar? It isn't found in the wild in this game — evolve Magmar.
Its base catch rate is 45 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Repeat Ball or Level Ball.
Evolution: Magby → Magmar (Level 30) → Magmortar.
Magmar in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)