Hello alle98,
Thanks for asking about putting the lost AirPods in Lost Mode.
Either, it's the fact they can't be found yet, which means offline, or they are an older version: Find your lost AirPods - Apple Support
"When you turn on Lost Mode for your AirPods (3rd generation), AirPods Pro and AirPods Pro (2nd generation), or AirPods Max, you can share a message with your phone number or email address."
The picture looks like both, no lost mode as they are older, and they are offline: "If your AirPods are out of range or need to charge, you might see their last known location, "No location found," or "Offline.""
Thanks.