How do I find the angle between 2 objects?

I need to find the angle between the player and an enemy so that the enemy can shoot at the player. I need to put in an angle of the bullet to travel, how do I find the angle?

From this page:

This is upside down, but should give you an idea for diagonals…

0 = right, 180 = left, 90 = down, 270 = up

You can also use ‘move object toward a position’ on the bullet and set the X/Y values to player.X(); player.Y()