YOU DON'T, you only find professer Rowan.
Prof Birch is NOT in Diamond Prof OAK is in Eterna City.
Go to Prof. Oak.
TO GET SHAYMEN IN LAND FORME
For the shinno pokedex, it is given to you from Prof. Rowan in Sandgem town at his lab. For the national pokedex, it is given to you from Prof. Rowan and Prof. Oak in Prof. Rowan's lab after completeing the Sinnoh pokedex.
If you have the National Pokedex, Prof. Oak will be in a house in southern Eterna City.
You can give it to a Porygon and trade it so it will evolve into Porygon2.
for one its Prof. Rowan and they are Piplup, Turtwig and Chimchar! hope i helped.
You can't catch Charizard in Diamond. You'll have to migrate or trade Charizard to get it in Diamond. You can have a Charizard in FireRed/LeafGreen and HeartGold/SoulSilver and X/Y, if you evolve Charmeleon. To get Charmeleon, you need to evolve Charmander or in X/Y you can find it at the Friend Safari. In FireRed/LeafGreen Charmander is a Starter from prof. Oak and in HeartGold/SoulSilver you can get it as reward from prof. Oak for defeating Red.
He is in Sandgem Town, in the Pokemon Lab after you see all the Sinnoh Region Pokemon.
complete a normal pokedex then go to palpark and talk to prof oak
To get the national dex, you first have to have SEEN every Pokemon in the regular pokedex. Then talk to Prof. Rowan.Then Prof. Oak will barge in say some stuff then he upgrades your Sinnoh pokedex to the Nationaldex
What to do after you talk to prof oak about groudon