How to calculate velocity for Basketball

I want to build a game where the avatar is controlled by the input of a Kinect v2. Also i want to design it as a basketball game, so the player picks up a basketball and throws it to the ring. But instead of giving the player the possibility to change the direction of the ball, i want to let them change the speed of the throw. For example if he quickly stretch the arm, the ball gets more power for the shot.

So i have the ball position, the target position (ring) and i have the speed the ball should be thrown. Also i set the angle to about 60°. So my problem is now, that i don't know how to calculate the velocity for the ball. If the speed was too low, the ball shouldn't go into the ring. Only if the speed is at a perfectly range. Is there any suggestion how i can achieve this?