[Evolution] Need filenames and comment for moving 8 years of Evolution mail to brand new flathub Evolution

[Lee McKusick <leemck gmail com>]

Hello Evolution List person. I am Lee McKusick a loyal evolution user.

I need a link to detailed instructions to find an Evolution email file
system that has "28 fields" and make it into an archive. Then I want a
link to instructions how to import that archive into Evolution 3.44.3
by Flathub.com.

The email file I have is stuck on an unmounted disk partition and I'm
not confident that I can figure out how to run the Evolution executable
that goes with that email file. The last runs of Evolution gave the 28
fields found 30 expected error and also email names and mail filters
were missing.

So far, this is the file I think holds the Evolution email:
~/.local/share/evolution/mail/local/cur/    ; What am I missing?

The Ubuntu evolution that came with Ubuntu 18 is:
evolution 3.28.5-0ubuntu0.18.04.2
The flatpack Evolution version is:
evolution 3.44.3 (by flathub.org)

I have been running Ubuntu Linux and Evolution Email for about 8 years.
For about the last year or so (2021) the Ubuntu 20.04 LTS has been
having problems with the sound software. At this same time, about 2021
Evolution email was working well. 

I appreciate the reliability of the Evolution email storage and search.
To fix my sound software problem, I decided to upgrade to the Ubuntu
22.04 a release candidate. Bad idea. I rolled back the entire system to
Ubuntu 18 and that Evolution 3.28.1-2 gave me an error message "import
failed found 28 fields expected 30. 

Thanks so much for some pointers to the details of moving my mail files
. Cordially yours, Lee McKusick