I highly recommend the QuickMigrations OST to PST Converter, a professional tool designed to efficiently convert all OST data into Outlook PST format. Its simple and intuitive GUI allows users of all skill levels to operate the software without any technical assistance.

The tool ensures 100% accurate data conversion, preserving the original folder structure of the OST file in the resulting PST, so all emails, contacts, calendars, and other mailbox items remain intact and organized.
https://www.goldytools.com/blog/how-to-convert-ost-to-pst/