You don't. Girafarig can only be obtained in Pokémon FireRed or LeafGreen by trading it in from another game. Or you can use this GameShark code:
17543C48 E65E0B97
41377A90 E36247DE
you cant go underwater in leafgreen!!
unown is it dums
Cerulean cave
find a peice pie
You must trade it from Pokemon firered or Pokemon leafgreen
Piplup does not exist in Pokemon LeafGreen or FireRed.
No, you cannot find cyndaquil in LeafGreen.
you should go to gamestop
LeafGreen version does not have Growlithe.
In the grass...
You cannot catch houndour in Pokemon leafgreen either get one from Pokemon emerald or Pokemon colosseum.
there is no such Pokemon
That item doesn't exist in leafgreen.
you can't catch aipom in leafgreen but you can get one from Pokemon colosseum or Pokemon emerald.
There aren't growlithe in LeafGreen. FireRed has growlithe, LeafGreen has vulpix.
it's in pokemon leafgreen
I don't really know about Pokemon leafgreen, but in Pokemon red you can get it in seafoam islands. Hope this helps!