Its impossible.
Although you may see your friends throw out Mew from time to time, and Mew up for grabes on the global trading system, it is impossible to catch Mew on Pokemon Diamond. This doesn't mean you can't have her on your game.
If you catch a mew on Pokemon Fire Red or Leaf Green, you can migrate it to your game if you have completed the game.
If You Meant To Catch To Mew,No.
No, you cannot catch a mew in Pokemon Platinum without cheating.
You cant catch mew.
You can't get mew in firered or leafgreen.
there no cheat to catch mew in pokemon ruby
a
no
Pokemon pearl
You need to trade Mew from Emerald
there is a mew in Pokemon soulsilver but you need to catch all leadndery Pokemon including event Pokemon
you can catch it in mt.cornet no cheat
you have to trade you cant catch it