put your emerald, ruby, saphire, leaf green, fire red, etc. game in the gba game slot of your ds. then when you turn you diamond/pearl game on and go to the continue/new game screen, there should be something that says: migrate from(the game u put in). press that, and choose the six pokemon you want to migrate. then once those pokemon are migrated, go to the migration station or whatever it's called. then you can go catch your pokemon!!
p.s.: please dont give me thumbs down, i am answering a request.