To convert your PST file to Thunderbird, use eSoftTools PST to MBOX Converter Software. PST files from Outlook can be easily converted to MBOX files. The easy-to-use interface. A demo version of the programme is available here, with a live preview of PST emails. Outlook 2019, 2016, 2013, 2010, 2007, 2003, and earlier versions are all fully functional. In this demo version, you can convert up to 25 emails per folder.
For more information:- Convert PST File to Thunderbird