You wanted to install npm 7.20.0, but the installed version is 6.14.13.
A common reason is an attempted "npm install npm" or "npm upgrade npm". As of today, the only solution is to completely uninstall and then reinstall Node.js. For a small tutorial, please see https://github.com/felixrieseberg/npm-windows-upgrade#usage.
I can't able to update npm
You wanted to install npm 7.20.0, but the installed version is 6.14.13.
A common reason is an attempted "npm install npm" or "npm upgrade npm". As of today, the only solution is to completely uninstall and then reinstall Node.js. For a small tutorial, please see https://github.com/felixrieseberg/npm-windows-upgrade#usage.
Please consider reporting your trouble to https://aka.ms/npm-issues.