laravel – "cross-env" is not recognized as an internal or external command, program or batch file executable

I am trying to execute the command: npm run watch to compile the files in laravel 5.6. I am using laragon that includes node js 8.9.

This is the error script:

$ npm run watch

> @ watch C:  laragon  www  learning
> npm run development - --watch


> @ development C:  laragon  www  learning
> cross-env NODE_ENV = development node_modules / webpack / bin / webpack.js --progress --hide-modules --config = node_modules / laravel-mix / setup / webpack.config.js "--watch"

"cross-env" is not recognized as an internal or external command,
Program or batch file executable.
npm ERR! ELIFECYCLE code
npm ERR! errno 1
npm ERR! @ development: `cross-env NODE_ENV = node_modules development / webpack / bin / webpack.js --progress --hide-modules --config = node_modules / laravel-mix / setup / webpack.config.js" --watch "` npm ERR! Exit status 1
npm ERR!
npm ERR! Failed in the development script @.
npm ERR! This is probably not a problem with npm. It is likely that there is an additional record output above.
npm WARN Local package.json exists, but there is no node_modules, did you want to install it?

npm ERR! A complete record of this execution can be found at:
npm ERR! C:  Users  Juanzu  AppData  Roaming  npm-cache  _logs  2018-11-21T22_07_58_504Z-debug.log
npm ERR! ELIFECYCLE code
npm ERR! errno 1
npm ERR! @ watch: `npm run development - --watch`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed in the @ watch script.
npm ERR! This is probably not a problem with npm. It is likely that there is an additional record output above.
npm WARN Local package.json exists, but there is no node_modules, did you want to install it?

npm ERR! A complete record of this execution can be found at:
npm ERR! C:  Users  Juanzu  AppData  Roaming  npm-cache  _logs  2018-11-21T22_07_58_582Z-debug.log

So I have my file package.json:

{
"private": true,
"scripts": {
"dev": "npm run development",
"development": "cross-env NODE_ENV = development node_modules / webpack / bin / webpack.js --progress --hide-modules --config = node_modules / laravel-mix / setup / webpack.config.js",
"watch": "npm run development - --watch",
"watch-poll": "npm run watch --watch-poll",
"hot": "cross-env NODE_ENV = development node_modules / webpack-dev-server / bin / webpack-dev-server.js --inline --hot --config = node_modules / laravel-mix / setup / webpack.config. js ",
"prod": "npm run production",
"production": "cross-env NODE_ENV = production node_modules / webpack / bin / webpack.js --no-progress --hide-modules --config = node_modules / laravel-mix / setup / webpack.config.js"
}
"devDependencies": {
"axios": "^ 0.18",
"bootstrap": "^ 4.0.0",
"cross-env": "^ 5.1",
"jquery": "^ 3.2",
"laravel-mix": "^ 2.0",
"lodash": "^ 4.17.5",
"popper.js": "^ 1.12",
"vue": "^ 2.5.7"
}

}