Mac OS X 10.10 (Yosemite) or later. The latest version of Mac OS X is currently 10.13 (High Sierra).
You can check your Mac OS X version by clicking the Apple icon in the very top-left of your screen. Then click, About This Mac. You will find the OS X version number towards the top of the opened window.
Microsoft Office (Word) 2011 or 2016. If you are subscribed to Office 365, then you have access to the latest version of Office 2016 for Mac.
Your Word icon should look like one of these (2016 left, 2011 right):