In Pokemon, Onix does not evolve at a specific level. The only way that Onix can evolve into Steelix is by trading it to someone while it is holding a metal coat.
level 19
36
at level 30
It eveloves at level 42
level it up to level 33
Drowzee evelove at level 26
if you trade it then you get dugdrion i think
at lvl.41
you evelove doduo at level 32
oddish eveloves at level 26 into gloom dbzpokeyu
Slugma evolves into Magcargo at Lvl 38.
Turtwig evolves at level 18 into Grotle, which then evolves into Torterra at level 32.