31 lvl.
you have to evolve aron to a aggron
Aron will evolve into Lairon at level 32, then into Aggron at level 42.
You have to evolve it from Lairon which you have to evolve from Aron. Aron can be caught in the grass patches by Fuego Fireworks by using the PokeRadar.
get to a certain level above aron and lairon
On level 32 he evolves into Larion. Source: Serebii.net
Use your poke radar at Fuego Ironworks to catch aron evolve Aron at level 32 into Lairon then 42 For Aggron
Your Aron will evolve at level 32 into Lairon.
Aron-->Lairon-->Aggron
You can find Aron only in Diamond.
level 32
Aron will most likely evolve at level 23 unless paralyzed
18