Instructions
Open the menu by pressing "X." Unlike in other Pokémon games, the menu appears on the Nintendo DS touchscreen instead of the top screen. You can use either the stylus or the system's buttons to navigate the menu.
Select the Trainer Card option on the menu's top right. The icon will be labeled with your character's name.
Check your Trainer ID. The Trainer Card appears on both of the system's screens; look at the bottom screen. Your ID number is located on the top left next to your character's name.