Can anyone help me to calculate the force to apply to a ball for reach a position? Here’s the scenario: my player is throwing a ball to an enemy. When he throws the ball he’s looking at the enemy (using LookAt) but the ball start from an offset from the player. If i apply a force Vector(0,0,50) (example) and then trasform it, the ball starts in front of the player but it doesn’t reach correctly the target enemy because of the start-offset 
Posting your source would help us give you a more detailed answer. I suggest that you have the ball look at the target and then move the ball forward on its forward. So right after you instantiate the ball:
ball.transform.LookAt(target);
ball.rigidbody.addForce(ball.transform.forward * 1000);
Note if gravity is enabled on the ball, it will hit low due to the pull of gravity.