Unfortunately, OST files directly store data for Exchange servers and can't be seamlessly converted to PST files (used for local storage). However, you can achieve a smooth migration:

Export from Outlook: Use the built-in Export wizard to selectively transfer data from your OST mailbox to a PST file within Outlook's limitations (2GB per file).

Third-party tools: Leverage specialized software with advanced features like filtering, deduplication, and bulk conversion for larger datasets and more control. some popular tools like Shoviv OST to PST Converter, Steller Converter for OST, SystoolsGroup OST Converter etc.

Network Upload & Import Service: For expert users, leverage Microsoft's service for efficient bulk imports, requiring administrative access and technical setup.

Remember, seamless conversion isn't possible, but these methods offer smooth migration alternatives!