How do you get mew in mystery dungeon red rescue team?

You can get Mew by connecting your GBA copy of Pokémon Mystery Dungeon: Red Rescue Team or Blue Rescue Team to a GameCube and inserting Pokémon Box: Ruby and Sapphire into the GameCube.

Once you've done this, you'll need to go into the in-game menu of Pokémon Box and select "Connect to Rescue Team".

This will allow you to transfer Mew from your Pokémon Box game into your Mystery Dungeon game.