Mew cannot be captured in "Pok?mon Pearl." The only game in which Mew can be captured is "Pok?mon Emerald," but it requires an event item that is no longer given away. You can still trade for Mew, but if trading is out of the question, there is only one method left. It requires access to a Nintendo Wii and the downloadable game "My Pok?mon Ranch."
Get access to a Wii, and purchase "My Pok?mon Ranch"
Whether by buying one, renting one or playing at a friend's house, access to a Wii is necessary. Purchase the downloadable WiiWare title "My Pok?mon Ranch" from the Wii Shop. "Pok?mon Pearl" has a connectivity feature with "My Pok?mon Ranch" that allows you to transfer your Pok?mon to it.
Catch 999 Pok?mon in "Pok?mon Pearl"
Transfer a total of 999 Pok?mon to the ranch. Of course, this must be done gradually. Up to eight different copies of "Pok?mon Pearl" can be used to interface with the ranch, so enlist friends with spare Pok?mon to help.
Find a Pok?mon Egg, and transfer it to the ranch
Once 999 Pok?mon have been sent to the ranch, it expands to its maximum level. At this point, the ranch owner Hayley asks for a Pok?mon Egg. Any egg is suitable. When it is brought to her, she gives the you her Mew in return.