Trouble Running Nodemon

New to node.js, Been trying multiple methods of running my index.js on nodemon.
To start I ran these commands in the terminal (chronological order):

1. sudo npm install nodemon -g
2. npm install --save-dev nodemon
3. nodemon index.js

This the error code I am getting:

jeff-tatlises193% nodemon index.js
Usage: nodemon [nodemon options] [script.js] [args]

  See "nodemon --help" for more. ```