There are several common scenarios where converting an OST file to PST becomes necessary—for example, when an OST file becomes inaccessible due to an unexpected power failure, Exchange Server crash, or changes in the Outlook profile that orphan the OST file. You may also need to convert OST to PST if you want to open an OST file from a different account in the same Outlook application.

Unfortunately, there is no built-in method to open or import an OST file directly into any version of Microsoft Outlook. In such cases, using a reliable third-party tool is essential.

I recommend downloading and installing the GoldyTools OST to PST Converter, one of the best solutions for effortless and accurate OST to PST conversion.

Key Features:

Quickly converts OST files to PST

Supports conversion to other formats like EML and MSG

Compatible with all Microsoft Outlook versions (32-bit & 64-bit)

Fully supports all Windows operating systems

With the free demo version, you can preview the first 25 items per mailbox folder, allowing you to evaluate the software before making a purchase.

https://www.goldytools.com/blog/convert-ost-to-pst-file-format-in-simple-steps/