Question: how to get mega stones in pokemon rumble world?
Answer: Once you reach Rank 33 and complete the challenge, you will receive the Stone Shop that lets you give a Pokémon a Mega Stone for 5 Poké Diamonds. Then, if you press the button with a Mega Evolution-capable Pokémon, a cutscene will occur where your Mii activates their Mega Ring and the Pokémon will Mega Evolve.