im making 2k cannon balls where do i get the mould?

If I'm not mistaken, I just talked to you in game and you said you got one...but if that was someone else, talk to the NPC whose name starts with an "N" on Ice Mountain.

yeah, it's some dwarf (naudorlf?), on ice moutain, he sells for 5 gp each, and you can buy more then one..., but yeah, he's up the ladder from the southern entrance of dwarven mines

You do need to do the Dwarf Cannon quest first, just in case that has not been mentioned. The dwarf won't sell the molds otherwise.

Nudolin on the Ice Mountain dwarf place. You need to do Dwarf Cannon quest first and the mold is pretty cheap

Dwaf Cannon Quest