You have to trade one from Emerald or Colosseum.
You cannot capture miltank in leafgreen only Pokemon colosseum can.
You can't find miltank anywhere on ruby only colosseum can get miltank.
I found the Pokemon "MILTANK" at route 38, 39, and 47.
Route 38
Miltank is a Normal type pokemon.
you can find miltank at route 209 with pokeradar (2%), and route 210 (south) also with pokeradar (2%)
route 209 and 210
Pokeradar on routes 209 and 210
Piplup does not exist in Pokemon LeafGreen or FireRed.
No, you cannot find cyndaquil in LeafGreen.
you should go to gamestop
Route 210 South (Poke-Radar)