External Microphone for iPad Pro 10.5?

I need to make screen recordings with audio with my iPad Pro (me lecturing while writing with stylus on PDF).

I can use PDF Expert and screen record it, but the audio is a bit quiet and variable.

Normally this doesn’t matter but with everything moving online-only I’d like to get slightly better audio.

IPad has 3.5mm jack and Lightning connection (no USB-C).

I have tried googling about external mics but rapidly got confused … even about what connection does an external mic use?

I don’t have a USB to digital AV connector, but I guess I could get one if that’s the best way to go?

Any suggestions gratefully received.