Hey, my name is Daniel (you can call me Lekrieg)
I can do the script with some comments to you or explain via chat what to do and you do for yourself, I can't help without knowing what you've done. Do you used the Navmesh component on the NPC or do you used some specific script for movement? Technically it is a simple task, but I need to see how you made the NPC movement.
You can send me a message and we discuss, if I can, I will do what you need without problem.