Unfortunately, an iPad Pro can’t be used to (directly) control the machine — it won’t function as a USB host device, and there’s no software in the App store for this sort of thing.
You can instead use a small single board computer and connect using a tablet interface such as: https://wiki.shapeoko.com/index.php/Carbide_Motion_Machine_Control_Software#Network_Connectivity
connect with a browser to port 8080
http://yourmachine_name_or_ipaddress:8080
I’d also suggest looking into Shapr3D and MeshCAM (some discussion of that here).
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