How to adjust the volume on Airpod Pro

If you have the 1st generation AirPods Pro, say "Hey Siri," then say something like "Turn up the volume" or "Turn down the volume." Or drag the volume slider in the app that you're listening to, on the Lock Screen, or in Control Center. You can also open Now Playing on your Apple Watch and turn the Digital Crown to make your AirPods Pro or AirPods (3rd generation) louder or quieter.

See Pause, skip, and adjust volume with your AirPods and AirPods Pro - Apple Support