To convert data from email clients such as Thunderbird, you can use the MailsDaddy Thunderbird to Outlook converter. It is a professional solution that helps you convert data from more than one email client. The software can be easily installed and run on any Windows-based system and can be converted to multiple email clients for outlaws. It helps in converting the data of Thunderbird MBOX and MailDIR format so it is a complete solution.
If you are looking for a trustful solution to convert the thunderbird files in the Outlook PST format, then you should check proficient third-party tools such as Stellar Converter for MBOX. This tool used an advanced mechanism in the conversion process. When I used this tool, I never faced any kind of problem during the conversion of multiple Thunderbird files into PST format.