I wouldn’t use that. After plugging in your mixer, in Audacity do a Transport > Rescan Audio Devices, otherwise just restart Audacity. Under Recording Devices in Audio Setup, you should see your mixer (It may be displayed as USB audio codec or somesuch - to be sure, it should go away if you unplug the device, then do a Rescan)
For recording channels, choose 2 (stereo) (or the maximum number available). It doesn’t hurt to to the scratch test (lightly scratch your fingernail across the grill of the microphone to be sure you have the right one).