Saving Outlook Live Mail Archived Messages

In days gone by I used Windows Live Mail and had two email accounts (let's call them email address removed for privacy reasons and email address removed for privacy reasons). Since I long since discontinued the someISP.net account I archived those msgs in Live Mail.

Then a while back I moved the email address removed for privacy reasons to office.365, but kept the Live Mail working so I could occasionally access info in the old someISP emails.

Now I want to fully pull the plug on Live Mail but want to somehow keep all those old emails.

What's a good way of doing this?