Power supply for Rasberry Pi can be found Power Supply.
PX4 system and Companion Computer (https://www.raspberrypi.com/products/raspberry-pi-4-model-b/specifications/) USB ports of Raspberry Pi (https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#universal-serial-bus-usb)https://www.raspberrypi.com/documentation/computers/os.html#gpio-and-the-40-pin-header
https://pinout.xyz/pinout/5v_power#
PX4 is configured by default to connect to a companion computer connected to the TELEM 2 serial port. No additional PX4-side configuration should be required if you use this port
username and password are admin.