To get Arcanine ex in the Fire Pokémon Mass Outbreak event, you’ll need to spend three Wonder Stamina and choose the Arcanine ex card through a Rare Pick when one appears. As with all types of Wonder Pick, you have a one in five chance of getting the card you want.

Pokémon TCG Pocket's Fire Pokémon Mass Outbreak event offers players a chance to collect rare Fire-type cards including Arcanine EX and Moltres.

If the first pack you opened in Pokemon TCG Pocket was the Pikachu pack, you were immediately rewarded with the Legendary Pokemon, Arcanine ex. Unfortunately for Arcanine fans, the fiery canine hasn't been a meta pick to build a deck around,