From the main screen go into settings – one option is software update (you need to know his apple I’d to do the update) also there is (from memory) an “about” option which has model number you can google that and you should get a page on Apple.com with generation info. FYI the more recent boxes are smal black ones, quite old ones (gen 1) where larger and white.
Apple updates software even on older boxes FYI but you’ll want the newer ones for latest features
If you have an iPhone Apple TV is great, you can browse content (mid week min movies, iPlayer etc) on phone and play it on TV. It’s good as a standalone unit for Netflix etc but not as powerful as when combined with a phone or computer