Node.js / npm: Can't find module when running in dev mode - node.js

Question

When running npm run dev, I got the following error message:
Error: Cannot find module 'webpack/bin/config-yargs'
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:571:15)
at Function.Module._load (internal/modules/cjs/loader.js:497:25)
at Module.require (internal/modules/cjs/loader.js:626:17)
at require (internal/modules/cjs/helpers.js:20:18)
at Object.<anonymous> (C:\Users\Isabelle\coursetro-eth\node_modules\webpack-dev-server\bin\webpack-dev-server.js:54:1)
at Module._compile (internal/modules/cjs/loader.js:678:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:689:10)
at Module.load (internal/modules/cjs/loader.js:589:32)
at tryModuleLoad (internal/modules/cjs/loader.js:528:12)
at Function.Module._load (internal/modules/cjs/loader.js:520:3) npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! coursetro-eth#1.0.0 dev: `webpack-dev-server --config build/webpack.dev.conf.js` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the coursetro-eth#1.0.0 dev script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
My enviroment is the following:
OS: Windows 10
NPM: Version 5.6.0
WebPack: Version 4.6
My package.json file:
{
"name":"coursetro-eth",
"version":"1.0.0",
"main":"index.js",
"scripts":{
"dev":"webpack-dev-server --config build/webpack.dev.conf.js",
"publish":"ngc -p tsconfig-aot.json",
"test":"echo \"Error: no test specified\" && exit 1"
},
"author":"",
"license":"ISC",
"description":"",
"dependencies":{
"web3":"github:ethereum/web3.js"
},
"devDependencies":{
"lite-server":"^2.3.0",
"webpack":"^4.6.0",
"webpack-cli":"^2.0.15",
"webpack-dev-server":"^2.11.2",
"webpack-validator":"^2.3.0"
}
}
What is this error about?