The way to obtain a Magmortar is by trading a Magmar holding a Magmarizer.
Magmortar is the final evolutionary form of the baby Pokemon Magby. In Pokemon Diamond, wild Magbys can be caught on Iron Island or Route 228. It evolves into Magmar at level 30 after which it can be traded holding a Magmarizer and it will evolve into Magmortar.
Trade a magmar with the magmarizer
You have to trade
The Magmarizer is a held item in the Pokemon games that helps the Pokemon Magmar evolve into Magmortar. This item can be found in Pokemon Diamond held by Magbys in the wild.
you must trade or migrate a magmar/magby from another DS Pokemon game or Pokemon ruby/sapp etc trade a magmar while it is holding a magmarizer for it to evolve into a magmortar
If you attach it to Magmar and trade it while it is holding the Magmarizer, it will evolve into Magmortar.
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.
machoke evovles into a machamp when traded magar evoles into a magmortar and an eletabuzz evoles into an electivire
after you finish the game go to volcano cave - magmortar will be there
You can find Pidey in a Pokemon Outbreak in Pokemon Diamond
There were 151 Pokemon on Pearl and Diamond both (including Manaphy), and there are now 210. Some of the new Pokemon include Froslass, Magmortar, and Rotom's new changing forms.
get it by evolving magmar