OP wrote:
"My iMac is on its last legs and I created email folders as backup for important stuff."
Do you keep a backup?
If not, time to start one.
My suggestion:
Get a Samsung t7 "Shield" SSD.
Then, download "SuperDuper" from here:
download (link)
SD is very easy to use. I don't think they could make it any easier.
It will create a "cloned backup" of your internal drive.
You should be able to boot from it, too.
SD is FREE to download and use.
However, if you want to do "incremental" backups, you have to register (not much $$).