Webpack 4.X NPM Run Start error

Package.json:

 { "name": "Webpack" ,  "version": " 1.0.0 " "description": " "main": " Webpack.config.js " "scripts" : { "test": " echo \ "Error:no test specified\" && exit 1 "" Build ":" Webpack " "Start": "Webpack-dev-server" },  "keywords" : [],  "author": "" " license ":" ISC " "dependencies" : { "jquery": "^3.3.1" }, " Devdependencies ": {" webpack-dev-server ":" ^3.1.5 "}}  

Bogon:webpack cristin$ NPM Run start

> [email protected] Start/users/cristin/documents/webpack
> Webpack-dev-server

module.js:487
throw err;
^

Error:cannot Find module ' webpack '
at Function.module._resolvefilename (module.js:485:15)
at Function.module._load (module.js:437:25)
at Module.require (module.js:513:17)
at require (internal/module.js : 11:18)
at object.<anonymous> (/users/cristin/documents/webpack/node_modules/webpack-dev-server/lib/ SERVER.JS:22:17)
at Module._compile (module.js:569:30)
at Object.module._extensions.. JS (module.js:580:10)
at Module.load (module.js:503:32)
@ trymoduleload (module.js:466:12)
at Function.module._load (module.js:458:3)
NPM err! code elifecycle
NPM err! errno 1
npm err! [email protected] Start: ' Webpack-dev-server '
npm err! Exit status 1
npm err!
NPM err! Failed at the [email protected] start script.
NPM err! This is probably not a problem with NPM. There is likely additional logging output above.

NPM err! A Complete log of the This run can is found in:
NPM err! /users/cristin/.npm/_logs/2018-07-23t03_08_57_715z-debug.log
Bogon:webpack cristin$ sudo npm install Webpack-dev-server
Password:
NPM WARN [email protected] requires a peer of [email protected]^4.0.0-beta.1 but none is installed. You must install peer dependencies yourself.
NPM WARN [email protected] requires a peer of [email protected]^4.0.0 but none is installed. You must install peer dependencies yourself.
NPM WARN [email protected] No description
NPM WARN [email protected] No repository field.

+ [email protected]
Updated 2 packages in 12.044s
Bogon:webpack cristin$

Webpack 4.X NPM Run Start error