SOS Encounter: Route 3 (15%)
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 Great Ball.
Evolution: Bagon → Shelgon (Level 30) → Salamence (Level 50).
Salamence in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)