Cannot find module '@babel/core'
Try running this.
npm install @babel/core --save
babel changed their package so your babel-core will not be the same as @babel/core.
Just for people who happen to drop by here, due to a recent major version update from babel 6 to 7, the babel-loader splits up into versions 7 and 8 respectively. If an accidental update to babel-loader 8 using "ncm -u" is causing this issue, just make sure you get babel-loader 7 by "npm install babel-loader@7". Installation instructions clearly noted here: github.com/babel/babel-loader – Thomas Cheng Sep 1 '18 at 16:46