You’ll need to get Pokemon black/white of black 2/white 2 doesn’t matter which one, beat the game in one of the versions of black/white and become champion, then head to route 15 and go into the pokemon transfer lab and talk to the npc that have a bit of a cutscene. Talk to the npc again to start the transfer process and with your diamond and pearl game make sure you have 6 Pokemon in the pc to transfer and a mini game will start where you need to catch them to transfer them. You can do this multiple times. Then transfer from whichever version of black/white to poketransfer and it would sent the pokemon in box 1 to pokebank then just move to home