How do you connect a USB MIDI keyboard to iPad pro?

This adapter may/might work, also.

https://www.apple.com/shop/product/MD821AM/A/lightning-to-usb-camera-adapter?fno de=91&fs=f%3Dadapter%26fh%3D4588%252B45b0

This works with my 1st gen 12.9 inch iPad Pro running iOS 10.3.3.

Not sure if this will work with a MIDI keyboard with any of the 2nd gen iPad Pro models.

The MIDI keyboard needs to use its own power, plus you will need this adapter

https://www.apple.com/shop/product/MK0W2AM/A/lightning-to-usb-3-camera-adapter?f node=91&fs=f%3Dadapter%26fh%3D4588%252B45b0