When 'npm run dev' I get this.
?  Command `hydrogen dev` not found. Did you mean `kitchen-sink prompts`?
>  (y) Yes, confirm
   (n) No, cancel
   Press ↑↓ arrows to select, enter or a shortcut to confirm.
Node and npm are up-to-date. I also tried opening a new terminal. I also tried deleting and rebuiding the storefront.
                        
I had the same problem, I just had to run
npm installin the package directory to install dependencies, then it worked.