How do I make a block point in the direction my mouse points?

I am making an artillery gun for my game, and so far it is working well, but I need it to be able to spin freely so the player can aim and hit his target. I only know the basics of Roblox Lua, but it was enough to make the weapon work. But I need it to turn, to point, in the direction according to the mouse pointer. Example, my mouse points in that direction, and the weapon turns, and it is pointed in that direction, so the player would use that to aim, and could shoot and hit his target. Since I don't know more than the basic Roblox Lua, I tried to look for something like this in the ToolBox, but all I found were the same scripts, which made your avatar's head spin according to the camera's position. The gun has a part in the middle of it, if someone can help with the script that does this for me, if I put it in this part, which is welded with the rest of the gun, will it still work? Please help this is practically the last step to build this model.

PS: this need to work, only if the player is seated at the seat.