I have installed Ubuntu Bash on Windows. I already have nodejs and npm on my windows machine at C:\\Program Files\\nodejs. In the bash she
nodejs
npm
C:\\Program Files\\nodejs
curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash - sudo apt-get install -y nodejs
this is enough, if you still face the problem
node installation needs restart, close you ubuntu window and start again it will solve your problem :)