Mathf.Atan2() will give you the angular direction of a delta between two cartesian points.
Mathf.Atan2() returns results in radians so be sure to multiply the result by Mathf.Rad2Deg to get it into degrees, if that is what you need.
Mathf.MoveTowardsAngle() helps you move on a 0-360 basis from one heading to another, taking the shortest way to turn towards it.
Also, please use code tags: Using code tags properly