You can easily convert Mac PST files using MacUncle PST to Thunderbird Converter. The tool supports Mac OS Machines.
Start MacUncle PST to Thunderbird Converter on your Mac Computer.
Select PST file using Add File(s) or Add Folder(s).
Choose saving format as Thunderbird from the option.
Mac PST to Thunderbird conversion process completed successfully, you can see the message of completion.