Don't worry about
files that say are reported as 'not 64-bit'. The problem will be for
applications that won't work in the
next mac OS; 10.
14. And that won't be a problem for you, at all,
if you don't upgrade your OS.
I would
not recommend upgrading to High Sierra
just for Word. First, there are too many alternatives, most of which are already 64-bit applications. Second, upgrading will guarantee additional load on your computer as each new OS is always larger and more powerful. Third, Apple makes it very difficult to upgrade to an OS earlier than the current one. It may not be easy to find a
valid version of 10.12. Lastly, the fewer problems you have, the happier you can be.
The major reason to upgrade/update your OS is for security improvements. Apple generally makes Security Updates only for the two previous versions of any OS. That means you probably won't be getting another Security Update. The secondary reason to upgrade is for the improvements in the OS and sometimes the apps that it can run (that need 64-bit architecture). Many folks are still using Mac OS 10.11, I only updated my mini to 10.13 because the mini died. El Capitan worked perfectly for me, but I have never used/owned Word.
Apparently, one can still download macOS 10.12.6 from the App Store.
This link will open the App Store at the Download page. DO NOT DO THIS UNTIL or IF YOU HAVE A BOOTABLE CLONE OF 10.11 ON AN EXTERNAL DRIVE OR A USB DRIVE. See
Jon's post above.
AppleMicrosoft has always treated the Mac/Apple as a second-class step-child and I don't think we can ever expect much more than that. They are, after all, a competitor. But there are several apps, usually free, that can open, create, save Word documents. Only one may actually be/need 64-bit architecture.
My suggestion about Word: If you make a living that requires sending/editing documents in Word, buy the latest version. It will simply be a tax write-off, anyway. If you are using it out of habit, create a new habit.
On the other hand, of course, are five more fingers! If your hardware is over six or seven years old, you may be forced to upgrade. And even if it is younger, things just break! The point is, when computers break, it is often best to simply replace with new models. If they are from Apple, they will come with the newest OS 99.9% of the time. As the old commercial used to say, "You can pay me now, or you can pay me later." Sooner or later, we
will pay!