The apt-get version of node is incredibly old, and installing a new copy is a bit of a runaround.
So here's how you can use NVM to quickly get a fresh copy of Node on your new Bash on Windows install
//switch to root
$ sudo su
//get NVM
$ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash