Thank you for your replies.
I tried Apple Pages to no avail. TextEdit opened on oldie I tested, but the result is very hard to read because the app changed the format and added and mixed in a huge number of irrelevant characters.
The error message says ". . . uses a file type that is blocked from opening this version." When I click on "Learn more about blocked file types," it repeats preceding quote, then says:
"If you can’t open a Word document that was created in an earlier version, first make sure the latest Office updates have been installed. Then, use the File menu to open the document. If that doesn’t work, use Apple TextEdit or an earlier version of Word to open it.
"Also, now in Word 2016 for Mac, you can open Word files saved in OpenDocument Format (.odt, .ods, .odp) and convert them to editable Microsoft OOXML files (.docx, .xlsx, .pptx ). You'll need to be connected to the internet to open ODF files and convert them to OOXML files. For more information on the conversion process, see
View OpenDocument Format (ODF) files in Office 2016 for Mac and
Why do I need the Microsoft online service to open some Office files?."
It doesn't seem the second paragraph applies. For the first paragraph: My Office is up to date, I checked. I tried to open from the File menu and got the same error message I quoted above. I addressed TextEdit above. I don't have an earlier version of Word.
It seems strange to me that Microsoft would create Word versions that make it impossible to open Word docs from much earlier versions. That must make hundreds of thousands of stored documents inaccessible.
If I were to try LibreOffice or FreeOffice, can I download only Word without the other apps in Office?