You may have seen the information about the changes to licensing for Teams rooms announced at the beginning of September 2022. If not, Tom Arbuthnot did a great write up on it on his blog.
Notifications are now rolling out into the Teams Admin Center for Teams Administrators letting them know about the changes.
If you have a Teams Room device on the older licence, going to the Teams Room pages under Teams devices in the Teams Admin Center, will trigger notifications.

There are two steps to the notifications. Step 1 offers a high level explanation of the two new licences

Step 1 of the tool tip reads:
Introducing new licenses for Teams Rooms
Microsoft Teams Rooms Basic is a free license for up to 25 rooms that delivers core meeting and management functionality for all Teams Rooms devices
Microsoft Teams Rooms Pro brings enhanced meeting experiences and advanced management and security to help you operate your devices at scale and enable inclusive hybrid meetings
Step 2 offers advice on viewing licenses on existing Teams devices.

Step 2 of the tool tip reads:
View license summary
View a summary of all your device licenses and filter devices by the license they’re assigned.
You can add, assign, and manage licenses in the Microsoft 365 admin center
When hovering over the license column where a device has a standard license the advice is to upgrade.

This notification from reads:
Microsoft Teams Rooms Standard
To use Pro features upgrade this device to a Microsoft Teams Rooms Pro license in the Microsoft 365 admin center before the current license expires.
The Learn More link here directs you to Microsoft documentation: Microsoft Teams Rooms license overview
There is also a warning banner at the top of the page advising an upgrade to pro licenses.

At the time of writing this upgrade option is not available but I understand that the option to upgrade is coming. This is usually done in the Product details page from the Microsoft 365 Admin Center under Billing -> Your Products. On the Product page there should be a link offering upgrades recommended for your org. Currently this is greyed out until upgrade is possible.

Accessibility note: The images included in this article are described in the article including text displayed on them and therefore no AltText has been added to the images. The images show the dialogs/tool tips/warning described in the article.