Today Apple released firmware version 2D15 for AirPods Pro. This will bring all customers to one update.
Until now, the AirPods Pro user base was fractured. Some users had firmware version 2C54 and others had 2B588. People with 2B588 complained that it weakened the Active Noise Cancellation feature of AirPods Pro.
Firmware updates to AirPods happens automatically, and there isn’t a way to manually do it. However, some people have found success by putting the AirPods in a case, connecting it to a power source, then re-pairing them to an iPhone or iPad.
In any case, you can easily check which firmware you have by going to Settings > General > About. Scroll down until you see AirPods / AirPods Pro. As you can see in my screenshot, I have yet to receive the update.