A couple ways of doing it, but the most straight forward is to go to
https://forums.androidcentral.com/e?...token=J15ozLw9, log in with your account, go to the Gear icon on the right (top, below your avatar), and select Settings. There a list of all of your devices should appear. You can select which ones appear in Google Play (in case you don't use any of those anymore) and rename them by clicking on the Edit button.
You can also do it by going into the same Gear icon, but instead of choosing Settings, select Android Device Manager. Those devices that are actively registered within the service will show up, allowing you to rename them by clicking on the pencil icon (Rename).