[NF]Converting Thunderbird email to ThunderbirdPortable email?

Anyone know how to do this? I was able to convert Outlook Express, no problem, works great.

I researched converting to ThunderbirdPortable and all the examples I found with Google don't work. There must be a way, export to something and then import?

--- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus