It looks like you might not have defined a start script in your package.json file or your project does not contain a server.js file.
If there is a server.js file in the root of your package, then npm will default the start command to node server.js.
You could either change the name of your application script to server.js or add the following to your package.json
"start": "node your-script.js"
Or you could just run node your-script.js directly
Hope it helps!!