It's surprisingly hard to find the right cable to hook up MIDI keyboards and a Nexus tablet.
You need a USB Micro 5 Pin Male to Type A Female M/F OTG Host Data Cable Adapter and then a regular Type A Male to Type B male USB cable.
You may not find them in stores so it's better to order online. Also be careful because a Type C USB cable looks very similar to a micro USB cable, but is different
THE MIDI ASSOCIATION (TMA)
The community of people who work, play and create with MIDI