you don't just find it. You have to catch a wild Pokemon that has it already.
http://bulbapedia.bulbagarden.net/wiki/Pokerus
there is no lilypad town in diamond
Unown, found Solacean ruins, directly east of Solacean Town.
Palkia cannot be found in Pokemon diamond, but after you beat the elete four if you go to celestic town the elder will show you a picture of palkia and you will have "seen" it.
Alamos Town does not appear in the Pokemon Diamond version of this game. It is in the movie, but not on this game.
No, they removed Lavender Town in Pokemon Diamond, Pearl, and Platinum.
Dawn can be found in Sandgem Town in front of Proffesor Rowan's lab
i think it is in the top of the tower near solaceon town.(the one with the daycare)
In Pokemon Diamond, the berry shop is in Floaroma Town.
Drifloon, He can be found on fridays in front of the house with the windmills near floaroma town.
Floaroma Town
At the end of Solaceon Town's ruins, it is one of the four items found there.
Pokemon Number 149 (Dialga) Cannot be found in Pokemon Pearl, he is only available in Pokemon Diamond, where as Number 150 (Paulkia) cannot be found in Pokemon Diamond. If you need to fill the spot to complete the PokeDex, you can see #149 from a lady in Celestic Town.