Escreva o próprio Nodemon no package.json

{
  "name": "abc",
  "version": "0.0.1",
  "description": "my server",
  "scripts": {
    "start": "nodemon my_file.js"
  },
  "devDependencies": {
    "nodemon": "~1.3.8",
  },
  "dependencies": {

  }
}
Aggressive Anaconda