Yes, mozbackup has been a problem for a long time. Does not work. You should be able to salvage much of what you have. If you post screenshots of the content as viewed in windows file explorer, I think we can point out what can be imported into a new profile. Merging doesn't work, but if you know what components you want, you can do this manually.

Hi I hope the following is what you require.

In thunderbird>profiles>w03saufb.default>mail there are lots of pop3.sa.exemail.com.au directories with suffixes '-1 to -17'.

inside these are files labelled inbox, inbox.msf. sent, sent.msf etc for drafts, trash and archives

i'm guessing extracting what's in these is what I want.

How to proceed?

Yes, actual message folders would be such as inbox, sent, drafts, etc. The files ending in .msf are just indexes and Thunderbird would rebuild automatically. The fact that you have folders with numbers indicates you have had multiple problems in the past. That is, when Thunderbird has a hiccup from such as an antivirus interruption, it creates a new folder. So, the folder ending in -17 would likely be the most current and its inbox, sent, etc. would be first priority to copy. To keep names straight, I suggest renaming them, such as inbox17, sent17. etc. Now, after setting up a new profile, exit TB and copy the desired items to the Mail\Local Folders folder. I suggest that because, when you reset the POP account, it may download messages that had been downloaded previously, depending on how many messages are saved on server.