Setup number series

Hello!
I’m trying out erpnext (15) at the moment and one of the first things I wanted to try was to setup number series for things like invoices.

I found this article that refers to this.

Unfortunately I can’t find the described possibility to set the number series and the second link doesn’t work.

This is how my settings page looks like. I can’t find anything that would bring me to something like “system” or “number series” (I tried Core/System settings without luck).

Document Naming Settings