An OST to PST converter is a computer program that can convert an OST file, a data file used by Microsoft Outlook to store emails, into a PST file. It's useful if you want to transfer emails from one computer to another or if you need to access your emails offline.
You can use a free online converter or download and install a premium converter on your computer. We always suggest using the Regain OST to PST converter.
If you decide to use an online converter, there are a few things that you should keep in mind. Make sure that the website is reputable and that it has positive reviews. Also, ensure that the website offers customer support.

https://www.regainsoftware.com/ost-to-pst-converter.html