Trouble with ionic start helloWorld blank

node -v : v8.11.2 (LTS)
npm -v : 6.1.0

ionic and cordova installed via npm.

when i type:
ionic start helloWorld blank

i got the following :

This is pretty nasty, but Ionic is tied to some very specific versions for dependencies.
I would suggest (if you are just starting) to clean up everything and re-install all dependencies strictly how Ionic Framework asks you to.