Scrivener 3 won't open old file, and conversion produces not-quite-empty project

Some time before 2013 (when my mother died), I transcribed a lot of my father’s letters to her from China/Burma/India (WW II) into a Scrivener project. I haven’t looked at it since. Best guess is early 2012. (I’ve been using Scrivener since about 2007? maybe early 2008.)

Today I wanted to access that material. Scrivener 3 couldn’t open it and offered to convert. Okay. BUT the result is a nearly empty nonfiction book template containing two files from the Seattle Times (only marginally pertinent; I may have put them there for a reason, although they are not directly related to the transcriptions; listed as *.webarchive).

I’ve attempted to look at package contents, on a copy of the backup (since I didn’t want to touch the actual backup).

No luck.

I’d hoped to find a folder with my files in it. I’m just seeing boilerplate within the appropriate file–i.e., setup as if for a blank nonfiction project (my name and address in place, but otherwise just placeholder text). All files are in the range of 4.8 - 4.9MB, which may simply reflect the Seattle Times pieces. Everything I transcribed would have been just text.

One of the reasons I’ve trusted Scrivener for so long is the ability to pull out files in a non-proprietary format, which I haven’t needed to take advantage of previously.

Thanks in advance for any clues you can offer to resolve this.