How to use iPad Pro with (LG) ultrafine 5k?
You do not need an adapter - you'll only need the USB-C cable that comes in the box with the monitor.

Note however that the iPad Pro (any model with USB-C) will only work at a 3840x2160 resolution at 60 Hz. I.e. you won't be able to take advantage of the full 5120x2880 capability of the monitor.

Also note that the monitor will only supply about 7.5 watts of power to the iPad Pro. This is usually not enough to charge the battery.

Note, the original LG 5k display is thunderbolt only, so if you done get a connection, check the model and firmware on your LG to be sure it supports USB. 


Difference between old and new LG UltraFine 5K(4K) Displays