Can't record from DJ mixer to Macbook Pro

So I am trying to record from a DJ mixer to Audacity - but seems to be a problem with the audio input.

I have a 2019 Macbook Pro, which has just one 3.5mm sound port. I’m running Monterey on it, OS 12.2.1.

The version of Audacity I have is 2.4.2

I have connected the mixer, which has a built in SoundCard (It’s an Allen & Heath Xone43C) from its Record outputs with a dual RCA cable to the Macbook - the other end of the cable is a 3.5mm stereo output jack.

But neither my computer nor Audacity seem to recognise it. Audacity just accesses my computer’s mono microphone, and records the sound of whatever’s in the room.

On its drop-down menu for Input sources next to the microphone, Audacity only gives me one choice: MacBook Pro Microphone.

When I go into my Macbook’s System Preferences, and through to Sound and then Inputs, the mixer does not show up. It seems to think the 3.5mm jack is simply a pair of headphones - it registers them as a potential output, but not as an input.

Not sure what to try next. Any suggestions very gratefully received. Cheers all

Apparently “Allen & Heath Xone …” has USB which connects to the computer …

As far as I know, the 3.5mm jack on the Macbook Pro is a headphone output only.
– Bill

That certainly looks to be the case on my MacBook Pro Bill.