You can see if you can download the Surface app from the Store. Link is here. There's an info tab that will say your model.
If the Surface app isn't working, you can get the model another way/
Right-click or long press on the Start button on the task bar and open a Command Prompt window. Type the following:
wmic computersystem get model
And press Enter. You will get the exact model name.
Surface 2 and Surface RT have no future path to upgrade from and are unfortunately dead. Sure, they can still be used, but there are no new features or apps for these Surfaces.
If it's a Surface Pro or Surface Pro 2, then it can still be updated to the latest build of Windows 10 without issue. You can download the media creation tool from here, run it on your Surface Pro, and you'll jump straight to the latest Windows!