Airpods
I lost 1 airpod from 2 sets opposite pods. Is there a way I can link them together in the same case
I doubt it. The serial numbers on both AirPods and case must match to work properly. That is why Apple needs to know the serial number when you order a replacement. See the 'Replace a missing AirPod or case' section in:
How to find your lost AirPods, AirPods Pro, or AirPods Max - Apple Support
"If you still can't find your AirPod or Charging Case, or if something is damaged, get the serial number and then contact Apple Support for a replacement. Then learn how to set up your replacement.
You can also learn more about AirPods pricing and service options."