Why error in Laravel Mix?

Question

npm

Hello. According to the video tutorial, I pulled the template on Laravel.
Laravel 5.4
Entered this code to compile js and css files into one file (webpack.mix.js file):

let mix = require('laravel-mix');

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.styles([
  'resources/assets/admin/bootstrap/css/bootstrap.min.css',
  'resources/assets/admin/font-awesome/4.5.0/css/font-awesome.min.css',
  'resources/assets/admin/ionicons/2.0.1/css/ionicons.min.css',
  'resources/assets/admin/dist/css/AdminLTE.min.css',
  'resources/assets/admin/dist/css/skins/_all-skins.min.css'
], 'public/css/admin.css');

mix.scripts([
  'resources/assets/admin/plugins/jQuery/jquery-2.2.3.min.js',
  'resources/assets/admin/bootstrap/js/bootstrap.min.js',
  'resources/assets/admin/plugins/slimScroll/jquery.slimscroll.min.js',
  'resources/assets/admin/plugins/fastclick/fastclick.js',
  'resources/assets/admin/plugins/dist/js/app.min.js',
  'resources/assets/admin/dist/js/demo.js',
], 'public/js/admin.js');
mix.copy('resources/assets/assets/bootstrap/fonts', 'public/fonts');

Then I went to the console and wrote this command: npm run dev
Then a lot of errors came out, here:

> @ dev /home/ssciiike/blog.glezer.ru
> npm run development


> @ development /home/ssciiike/blog.glezer.ru
> cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js

sh: cross-env: команда не найдена
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! @ development: `cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the @ development script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/ssciiike/.npm/_logs/2018-07-05T16_13_00_006Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @ dev: `npm run development`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the @ dev script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/ssciiike/.npm/_logs/2018-07-05T16_13_00_023Z-debug.log

I work on Linux Mint, the Project is hosted. I searched for a solution for a long time, but did not find it, I tried deleting the node_models folder, etc., but it did not help. Also, tell me how to install this folder back? or you can do without it