You may already have read up a bit on this but here is a link:
Bladder Stones (Urinary Calculi) in Dogs
There is sometimes an alternative to surgery and that is the dissolving of the stones, but again your vet needs to assess the urgency of the blockage.
He is very very young to have stones. Have you done a BATS test? And or a liver panel profile?
Also he should have pre-op blood work. Now I know you are in Bangladesh, and I am assuming this is India, so I really don't know in India what the vet practices are like, but I am hoping they have teaching hospitals and vet specialists there. You need to go to an internal medicine specialist ASAP if you are not already there.
I pray for you and your pup as this is quite a serious condition. Please keep us updated and if we can help in anyway we will.