You can't get nidoran in emerald only in firered and leafgreen.
Only On FireRed LeafGreen.
At The Pokemon Safari In Fuschia City
You can find Nidoran in route 3 (sometimes even Nidorino\Nidorina) and the Safari Zone in Fuchia city.
You can catch her on route 103, really rare though so look hard! :)
Nidoran evolves when he or she reaches level 16.
You can't get nidoran in emerald only in firered and leafgreen.
There are two nidoran's male and female both can be found in various spots notable areas are: The route west of viridian city and the safari zone (central area).
Only On FireRed LeafGreen.
Lv.16
Goldeen/Seaking, Nidoran/Nidorino, Nidoran/Nidorina and Rhyhorn/Rhydon learn it.
Nidoran Male and Female can be found in these places: The route west of viridian city and the safari zone.
At The Pokemon Safari In Fuschia City
You can find Nidoran in route 3 (sometimes even Nidorino\Nidorina) and the Safari Zone in Fuchia city.
Try looking on the route west of viridian city.
There are a bunch of Pokemon that can evolve: Nidoran, Pidgey and plenty more.
trade a nidoran male from firered or leafgreen to sapphire then evolve it at level 16.