Open the Aurora Remote Control software and click File > About Aurora Mixer to display the current Firmware Rev. If connected via AES16e or Thunderbolt, instead use the Lynx Mixer and click Mixer > About. Alternatively, you can power the Aurora on by pressing the TRIM and POWER buttons at the same time.This will put the unit into "Vegas" mode, where the front panel LEDs flash from left to right.
In the METER display, one number on the IN row and one on the OUT row will flash more quickly.
These numbers together reveal the firmware revision. If it is "1" on IN and "8" on OUT then you have rev 18. "2" on IN and "4" on OUT, that means 24.