How would I make desiredangle face the position of players mouse?

So I have a Motor6D that connects to both player arms and a torso and I am trying to make the motor change so that it faces the position of the mouse. I tried changing the C0 of the motor to make it face the (mouse.Hit.p - torso.Position) vector, however that didnt work and the motor was facing the completely different direction. So since I needed to only change the Y axis of the motor I thought that it would be better to use desiredangle property of the motor. However I dont know how to make the desiredangle point to the direction where my mouse is facing and I need help.