XYZ Coordinates, 360 Rotation.. How to calculate? AutoIT Visual Basic, Visual Studio

Hello! Ive got a homework assignment for my game Dev. class, and the assignment is to find XYZ coordinates of the player (which I have now) then map out a path with the XYZ Coordinates, while writing the XYZ coordinates to a Config.ini file every .5 seconds for later use, So I have that part down pack, im able to record player movement through XYZ coords to an config.ini file, But now Im stuck at the last part of the project!

We have to take the recorded path coordinates we recorded and read from the .ini file, which isnt the the problem., my problem is player rotation! Im wondering how do you calculate which way the player would have to turn to goto a certain coordinate, (like a GPS points to a saved coordinate)  So theres a 360 Degree rotation, and say the next coordinate the player needsw to walk to is X:-6381 Y: 471 Z: 378 (These are rounded to the closest integer) So how do I calculate which way or how much the player needs to rotate to move in that direction?!
Thanks so much in advance for the help, Im enjoying my stay here.

Also, Im programming this in AutoIT V3 Beta since its an open "Freestyle" project, But if someone knows how to do it in Visual Basic, C++ or C# ill understand any of those, doesnt need to be strictly an AutoIT answer, Thanks.

p.s, Ive heard it would be easier to use 180 Degree rotation for the calculation of player rotation.... Let me know your opinion. Thanks alot

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AutoIT V3 BETA - $PlayerRotatiion = ?
Visual Basic - Dim playerRotation = ?
C++ - player rotation = ?
 
please help! :p