you get it by finding all the Pokemon in the sinnoh pokedex.remember that u don't have to catch them for it to count in your pokedex
if you don't know who your missing you're probably missing 152 rotom in the old chateau in eterna forest or dialga and palkia you get the orbs by going to this one cave in mt. coronet and there should be 2 pokeballs in it and a rock the 2 pokeballs should be the orbs andd the rock should be an item. after that you can go to spear pillar and catch both of them
In Platinum dex' its Dusknoir in National dex' its Sunkern.
In Pokemon Platinum to get the National Dex you will need to have seen all 210 Pokemon in the Sinnoh Dex then talk to Professor Rowan and then after a while Professor Oak will give you the National Dex!
go and see all the Pokemon in the sinnoh dex
You complete the shinho dex first and then you get the national pokedex
According To The Platinum National Dex, Lickitung Is #108.
In Pokemon Platinum Version, there are two Pokedex'es, the Sinnoh Dex, and the National Dex. In the Sinnoh Dex, the 151 Pokemon is Manaphy. In the National Dex, the 151 Pokemon is Mew.
spiritomb in the sinnoh dex lickitung in the national dex
National Dex: Igglybuff Sinnoh Dex: Togetic
Cranidos in the Sinnoh Dex, Fearow in the National Dex
The next Pokemon after weavile is magnezone in the national dex
The sinnoh dex has 210 pokemon, and the national dex has 493 pokemon. It has an entire 664 pokemon (I think)
in sinnoh dex it is togetic but in national dex it is igglybuff