How to turn a character?

How to turn a character so that the left hand is equal to the position of the target
You can see on the photo below. The model looks to the left. I want the rifle barrel to be equal to the crosshair position only when the player presses the right mouse button.

I only don’t know how I can rotate this model.
Please help me.

Look into IK in the documentation. Should lead you to the answer you need.