Hi Leo,
Excellent question!
The PiicoDev connections assume that you are using I2C0 which is pins GP8(SDA) and GP9(SCL), and power is 3v3 on the RPi Pico expansion board, you can checkout the product page here:PiicoDev Expansion Board for Raspberry Pi Pico - Adapters - PiicoDev Australia.
A good reference is the pinout reference card that you get occasionally in Core orders.
I dabbled in something similar for a macro keypad using Adafruits mechanical variant (much like the new Core smart modules). High pitch screeching coming from a board - #3 by Liam120347
