First update the Debian apt package repository to include the NodeSource packages:
$ curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
Now that we have added the NodeSource package repository, we can move on and install Node.js!
$ sudo apt install -y nodejs
After it finished validate install by typing:
$ node -v
You should get a response like "$ 12.10.0". Now you are good to go to run npm.