https://angular.io/guide/setup-local#create-a-workspace-and-initial-application

node version v12.20

npm version v6.14.8

Already installed - npm install -g @angular-devkit/core --save-dev

i followed the steps to create a angular app but below error comes

ng new my-app

(node:9292) UnhandledPromiseRejectionWarning: Error: Cannot find module '@angula r-devkit/core' Require stack:

• C:\Users\user_name\AppData\Roaming\npm\node_modules@angular\cli\utilities
  config.js
• C:\Users\user_name\AppData\Roaming\npm\node_modules@angular\cli\lib\init.j s