When I change the file format to .lwp my text editor adds an invisible .txt extension to the file name (e.g.: filename.lwp becomes filename.lwp.txt) and I can’t see anyway to make it stop doing that.
Lucy
Try putting quotes around the name. In Windows, at least, that keeps it from adding .txt at the end.
Okay. Maybe this will help - when I try to open a file with Pages, I get the following error message:
[filrename.txt] can’t be opened right now.
Text encoding Western (Windows Latin 1) isn’t applicable.
Does that have any meaning in this?
Lucy
My mistake.
I was thinking about BBedit’s search and replace, which uses grep to do the matching.
An easier way to do that is use the strings command, which extracts any printable text out of binary files:
I would take advantage of @AHunter3 's generous offer 
I myself do not have a copy of Word Pro, therefore cannot verify any solution.
However, if all else fails, “stripping out the codes” is automatic, using e.g. the strings command in the Mac terminal. You definitely do not have to spend any time doing it manually.
Well, it was worth a shot. Thanks to everyone who offered suggestions, and especially to you & @AHunter3, who got me to thinking about my computer nerd cousin who still has a PC running a working version of Word Pro. I sent him a couple of files and he spent a couple of hours trying to open them in various ways and concluded that they truly are just text files full of coding symbols. I only have a few more files to strip, and, now that I’m retired, more than enough time on my hands to do the task.
Again, thanks to everyone.
Lucy
If you go into file explorer, and click on the filename so it allows you to edit it, then change the extension, that should actually change the extension. (Giveaway it worked is when it warns you changing the extension means the file may not work with certain programs)
The problem is if you open the file with, say, Notepad, then try to save it - who knows what Notepad adds to the file or how it messes up the codes (Theoretically not much, but who knows). The above suggestions to recover work best if you still have the original LPF files and simply renamed them to TXT. Saving in, say, Notepad - could cause the program to alter codes on saving which it does not think are compatible with actual text documents.
I know the OP said this is on a Mac, but in Windows File Explorer there is an option to hide extensions for known file types. It’s checked by default but I always turn it off because I want to see the file extensions. If the option is checked, and you create a new text file and name it, say, “readme.txt”, Windows will actually name it “readme.txt.txt”, except you won’t see the second “.txt” displayed onscreen.
Apparently this is also true of MacOS.
Filename extensions are usually hidden in macOS