Instructions
Insert a Game Boy Advance "Pokemon" game into the Game Boy Advance slot of the Nintendo DS, located on the top of the system. Place "Diamond" into the DS slot of the Nintendo DS, located on the bottom of the system. Turn on the system.
Select the "Migrate from..." option on the main menu screen to transfer Pokemon from the Game Boy Advance game. You can select up to six Pokemon at once to transfer. After you have transferred Pokemon, load your saved "Diamond" game to play.
Travel to Pal Park, located on Route 221. This route is located in the Sinnoh region, east of Route 220. You will be given 30 Park Balls at Pal Park and set loose in its regions.
Wander about the area in pursuit of your transferred Pokemon. Pokemon will wander in areas of the park that fit their nature. Water-type Pokemon, for example, are more likely to be found in the pond region of Pal Park.
Enter into random encounters. If you encounter one of your transferred Pokemon, use the Park Ball to capture it. Park balls cannot fail when thrown and there is no need to weaken the Pokemon first. If you capture all of your Pokemon within a particular time limit, you will receive a prize from Pal Park.