Routes,38,39,and 47.
You'll have to look for about 5 min because they're kind of rare.
Milktank can't be evolved .
First, head west of Ecruteak City. From there, you will reach a large, grassy patch. Miltank can be found there. You cannot catch the miltank on the farm.
oran berries
use a strong attack like slfdestruct
You can find it in a house on the route just above olivine city.
go to moo moo farm and give the miltank 7 oran berrys and they will give you one
give the sick miltank 9 oran berries talk to the girl on the left and she will give you seals and the seal case
You keep collecting berry and feeding the miltank with them eventually after about ten berrys the miltank will get better
Whitney uses Clefairy and Miltank in Pokémon Gold/Silver/Crystal/HeartGold/SoulSilver and in the anime she has a Nidorina, a Clefairy and a Miltank.
You randomly get them from a little girl in the right-most house in Olivine City once a day. You must have the Capsule Case first, which you get from feeding Oran Berries to the sick Miltank at the farm on Route 39.
I think 252 Including Celebi And The Egg of Ushie And Miltank....
in soul silver