I am having issues running PUG

Please look at my code and tell me what I am not seeing... I installed PUG ..

i am getting the following error:

Error: Cannot find module 'pug' at Function.Module._resolveFilename (internal/modules/cjs/loader.js:580:15) at Function.Module._load (internal/modules/cjs/loader.js:506:25) at Module.require (internal/modules/cjs/loader.js:636:17) at require (internal/modules/cjs/helpers.js:20:18) at new View (/Users/marlene/node_modules/express/lib/view.js:81:14) at Function.render (/Users/marlene/node_modules/express/lib/application.js:570:12) at ServerResponse.render (/Users/marlene/node_modules/express/lib/response.js:1008:7) at app.get (/Users/marlene/expressPractice/app.js:8:6) at Layer.handle [as handle_request] (/Users/marlene/node_modules/express/lib/router/layer.js:95:5) at next (/Users/marlene/node_modules/express/lib/router/route.js:137:13)

Here is my code app.js

var express = require('express')

var app = express();

app.set('view engine', 'pug');

app.get('/', (req, res)=>{
 res.render('index'); 
});

app.get('/hello', (req, res)=>{
  res.send('<h1>Hello,  javascript developer!</h1>')
})

app.listen(3000, ()=> {
  console.log("the application is up and running on local host 3000")
}); 

index.pug

doctype html 
html(lang='en')
  head
    title
  body
    h1  the future of something magical 
    p  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus at neque nibh. Ut feugiat erat in orci varius, eu porta odio maximus. Nulla posuere nunc finibus hendrerit porttitor. Quisque eu porta odio, et eleifend dui. Aliquam feugiat nunc eget velit scelerisque, quis consectetur nisl placerat. Vivamus aliquam sem eget viverra consectetur. Etiam rutrum enim sed nulla malesuada auctor.