The NPM team officially recommends this method of updating Node. (source below)
First, open PowerShell as administrator and run the following command.
Set-ExecutionPolicy Unrestricted -Scope CurrentUser -Force npm install -g npm-windows-upgrade npm-windows-upgrade
You will be prompted to select a version of NPM to install. Use arrow keys to move up and down and choose the version you want to update to and press Enter.
If your upgrade is successful, you should see something like this.