Pin mappings of the 30P base extension

I have a few of questions about the 30P base extension:

(1) I want to control a stepper motor via the E0 Stepper pins of the 30P base extension but the developer guide does not list where those pins are. Can someone enlighten me?

(2) I want to use the stepper to control a linear actuator that functions as a syringe pump. Similar to this project: https://www.instructables.com/OpenLH/ but done via Python, not Blocky. I figure I can power the stepper via the 12V output of the front extension port and use Gcode commands to deliver different amounts of liquid while in S2 (3d printing) mode. How can I do that via the uArm-Python-SDK?

(3) Where can I obtain a 30P Bottom Expansion Board?

Thanks