Connecting a MIDI piano keyboard to the iPad with a MIDI cable
The cable you have is actually not a MIDI cable - it is however the correct cable for many keyboards/stage pianos today. The standard MIDI plug looks quite different (it is round), but in the end you'll be able to transfer the same data over the USB cable you have.
The adapter you need depends on which version of the iPad Pro you have. For the older ones with a Lightning port, you can use for example the Apple Lightning to USB Camera Adapter. For newer iPad Pros with a USB-C port, you can use for example the Apple USB-C to USB Adapter.