How to import Microsoft® Outlook 2013 Email messages to Mozilla® Thunderbird

Thanks. Does this work for all my PST files? I have 7 email accounts in Outlook and 6 PST files for storing old emails. How do the emails get split? Each to their own folder?

Outlook is grayed out. This no longer works.

How it is possible without format conversion?
MS Outlook supports .pst format while Thunderbird supports .MBOX. I did this conversion through Stellar PST to MBOX converter software.