Things You'll Need
Instructions
Find a copy of "Pokemon LeafGreen," "FireRed" or "Emerald" for the Game Boy Advance that has the Mew Pokemon captured.
Defeat the Elite Four and encounter 150 different Pokemon in your copy of "Pokemon Pearl/Diamond" and talk to Professor Rowan in Sangdem Town to get the National Pokedex.
Save the game and turn the console off. Insert the Game Boy Advance game pack with Mew on it into the Game Boy Advance slot on your Nintendo DS. Ensure that your copy of "Pokemon Pearl/Diamond" is inserted in the DS game slot.
Turn the console on and load "Pokemon Pearl/Diamond." At the main menu, select the option to migrate Pokemon from your Game Boy Advance game. Choose Mew and five other Pokemon from the Game Boy Advance game to migrate, and then confirm your choices.
Load your game from the main menu and travel to the Pal Park on Route 221.
Talk to the Pal Park ranger inside the building and collect the six "Park Balls," then go through the door behind him to enter the park.
Go to the top left corner of the park and walk around the long grass in the forest area to encounter Mew.
Throw a "Park Ball" at Mew to capture it. Continue to hunt and catch the other five Pokemon you migrated to the Pal Park.