To get the Pokemon TCG Pocket Mew card, as mentioned above, you need to complete the Kanto Pokedex, which means getting at least one of every of the original 150 Pokemon in the game. Once you do so, an option will come up in your "missions" tab to complete the quest and reward you with the Mew card itself, like any other mission reward.

All of the Secret Missions inCG Pocket listed, including the cards you need, and their booster packs, for the Pokémon Pocket Secret Missions.

Pokemon TCG Pocket has seven Secret Missions in total, and here’s a list of all of them, including how to complete them and their rewards.