You go to Fuego Ironworks.
magmarizer and electrizer don't come until diamond and pearl
You can't. On Diamond, Pearl and Platinum there is a 5% chance that Magby will hold the Magmarizer.
Migrate it.
Trade a magmar holding a magmarizer and to get that you have to catch a bunch of magby which I think you can only catch in Diamond.
there are 150 kinds of Pokemon that you can see and/or obtain. Unless you have friend trade you Pokemon that you can only get in pearl to you, you'll never obtain them all. In Pokemon diamond and pearl all you have to do is see the Pokemon and you get its data unlike the older versions where you have to obtain them.
Magby requires Level 30 to evolve into Magmar and then trade it while holding the Magmarizer to evolve Magmar into Magmortar in Pokemon Diamond/Pearl. Magby can be found on Route 227 in Pokemon Diamond.
darkrai and arcus
Milktank is located in route 209 and 210 in both Diamond and Pearl.
No, you do not need diamond and pearl to obtain all the Pokemon in the national pokedex. You either need to have a friend who has all the older Pokemon, or you could transfer the Pokemon yourself from older games.
IT IS NOT IN POKEMON DIAMOND OR PEARL BECAUSE IT IS ONE OF THE STARTING POKEMON IN LEAFGREEN!!!!! Migrate one from firered or leafgreen.
you cant, you need to trade one from pearl or diamond
Bonsly is located in the trophy garden in Diamond and Pearl as well as routes 209 and 210 for Pearl.