Damage direction indicator on screen.

I am trying to make an indication on the screen showing the direction of incoming damage.

Finding the direction of the incoming damage is not a problem.

Code (CSharp):

1.     public Vector3 DamageDirection(Vector3 targetLocation, Vector3 damagerLocation)
2.     {
3.         var heading = damagerLocation - targetLocation;
4.         heading.z = 0;
5.         var distance = heading.magnitude;
6.         var direction = heading / distance;
7.         return direction;
8.     }

This is where I am having problems.
So I have a UI image on the screen with the anchor in the middle of the screen.
I have no idea on what maths I need to do to change the UI images rotation.z to make it point in the direction of the damage.
I have looked through many other threads on this matter, but non of them have been what I have been looking for.

I think the main problem I am facing is converting a vector 3 to a Quaternion.
Any help would be appreciated.

 

So far this has worked for me for rotating objects in general:

Code (CSharp):

1. transform.rotation = Quaternion.LookRotation(forward, up);

forward is where the blue axis should point, and up is where the green axis should point.