I came across your above question and it is related to my skill set so I will help you in resolving your issue. You just need to follow below steps.
1.You need to install your nodemon globally using below command:
C:\>npm install -g nodemon
2.Then type below command to get prefix:
C:\>npm config get prefix
After the command executes successfully you will get the output like below in your console:
Just Copy it.
3.Now you need to Set Path by following below navigation.
Go to your Advance System Settings → click on Environment Variable → Click on New (Under the User Variables) → Then it will display the Pop up form → just Pass the below values:
4.variable name = path,
variable value = you need to Copy output from your console
5.At the end just Run Nodemon: