You can find it in a house on the route just above olivine city.
give the sick miltank 9 oran berries talk to the girl on the left and she will give you seals and the seal case
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
Routes,38,39,and 47. You'll have to look for about 5 min because they're kind of rare.
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.
go to moo moo farm and give the miltank 7 oran berrys and they will give you one
Heal the sick Miltank at the Miltank Farm and talk to the girls.It should take 7 oran berries.Go north of olivine city and go inside moomoo farm.Give seven oran berries to the sick miltank,and the girl on the left will give you the seal case.if you want seals,go to olivine.on the right of the poke mart go north.there are two houses go inside the house on the right (closest to the lighthouse) and talk to the little girl.she will give you three random seals a day.hope i helped!(You will need to use 7 Oran berries to heal the miltank)In soul silver you get the seal case from one of the twin sisters in moo moo farm (north of olivine city) after you heal the sick miltank using oran berries.
You keep collecting berry and feeding the miltank with them eventually after about ten berrys the miltank will get better
In the house on the route above olivine city.
first go to the miltank cottage give the sick miltank about 4 or 5 oran berries and then talk to the girl on the left of it