I am struggling to find this file to download.
#include<AFMotor.h>
or just AFMotor.
Adafruit Motor Shield library from the library manager.
Use at your own risk.
You need to post all the code in code tags. A single .h file is useless; it may be used in hundreds of places. Where did you get the containing sketch? Do you have to use that sketch? Why not use the Adafruit or a similar established library?
Don't worry. I have figured it out. that file had to be replaced a few years ago, so i used a different one in the code instead. I did a lot of research to figure that out.