how to

You have to see all of the Pokemon in the Sinnoh dex to migrate pokemon. not the national dex. That would be impossible without migrating. The national dex includes all Pokemon from all of the Pokemon games.

And it is possible to see all of tme in either pearl or diamond without trading at all. You just have to visit every trainer, battle the E4 and get shown a photo of palkia or dialga depending on the game you have.

To get the National Pokedex, you must see all 150 Pokemon in Sinnoh, whether it be by battling trainers, seeing them in the wild, or evolving your Pokemon, it does not matter. You just have to find all 150 Pokemon in the Sinnoh pokedex in order to get the National pokedex. When you see all 150 Pokemon, go to Professor Rowan's office, and talk to Professor Oak, he will give you the national pokedex. Hope this helps.

You have to complete the first pokedex then you can migrate. You can use a arp code and get a level 100 arceas but if complete the first pokedex and get the 2nd 1 you can catch any pokemon.

You have to see all of 150 Pokemon in Sinnoh.I would try to trade a lot but you do not have to trade to get all 150 Pokemon.If you have Wi-Fi that would also help a ton cause most of the time you won't know where in the game they're at. After you see all the Pokemon in Sinnoh see Proffeser Rowan.Hope I helped!