[imrahil_SVK]

2NH4NO3 + K2SO4 = (NH4)2SO4 + 2KNO3 

or give me another recipe to make KNO3 pls

[Arkcon]

Buy it, or take secondary school level chemistry.  Somehow you're under the impression that this group will give you free explosives component manufacturing advice.  You are, quite simply, mistaken. 

Commercially, the stuff was mined, or made by neutralizing potassium hydroxide with nitric acid, which is made from ammonia, which is made from nitrogen and hydrogen.  But, at each step, the devil is in the details.  Basically, each raw material is mined, then purified, then reacted.  You can learn a lot of useful chemistry, trying to track the whole procedure.

[hmx9123]

While I question why you are wanting to make potassium nitrate, the reaction you present relies upon solubilities, just as the analogous reaction you presented in the citizen chemist forum trying to make KOH.  If you're really interested in methods of selective precipitation and equilibrium, I'd be happy to work with you, but you have to show us that you're actually attempting to work this problem and not just be a troll wasting our time answering meaningless and ultimately completely undefined questions.

And why on earth you'd have an easier time locating ammonium nitrate than potassium nitrate is beyond me.

[AWK]

2NH4NO3 + K2SO4 = (NH4)2SO4 + 2KNO3 

or give me another recipe to make KNO3 pls

Look at solubility of all compounds at RT and say 100 C, and decide if this method is possible. In my opinion there is no chance.