Hello
It depends on your current certification status. If don't have any certification, you don't even have to bother about Windows Server 2012 exams, and you can directly go for Windows Server 2016 (70-740) or any other exam you have prepared for.
On the other hand, if you already have a certification, you may need to go for the Upgrade exam(s), and the exam again depends on your current certification level.
Nevertheless, both Windows Server 2012 and Windows Server 2016 make you MCSA depending on what exams you pick and which ones you've already cleared.
You can always go to https://mcp.microsoft.com/mcp, sign-in with your MCP ID, and go to Certification Planner from the Dashboard to know the path you should take.
Cheers!!