This is the new best way to upgrade npm on Windows.

Run PowerShell as Administrator

Set-ExecutionPolicy Unrestricted -Scope CurrentUser -Force
npm install -g npm-windows-upgrade
npm-windows-upgrade

Note: Do not run npm i -g npm. Instead use npm-windows-upgrade to update npm going forward. Also if you run the NodeJS installer, it will replace the node version.

• Upgrades npm in-place, where node installed it.
• Easy updating, update to the latest by running npm-windows-upgrade -p -v latest.
• Does not modify the default path.
• Does not change the default global package location.
• Allows easy upgrades and downgrades.
• Officially recommended by the NPM team.
• A list of versions matched between NPM and NODE (https://nodejs.org/en/download/releases/) - but you will need to download NODE INSTALLER and run that to update node (https://nodejs.org/en/)