You can only use a certain node-sass version range with a specific Node.Js version.
So if you're you are using Node 12 - you must update to [email protected] etc
This should get rid of the errors.
This is explained in the repos FAQ:
https://github.com/sass/node-sass/blob/master/TROUBLESHOOTING.md#404s
Either try with:
Quotenpm install -g npm@latest