I suggest that the OST file can be converted to PST using the SysInspire OST to PST converter software.
I had tried many methods and even different third party software, even the manual methods were so irritating and total trash and saddened me a lot.
SysInspire is known to be the most renowned name in the field of ost to pst conversion.
The SysInspire OST to PST converter software is a best-rated software which is used to restore all the emails from the OST file and export them to Outlook PST format.
The software has advanced search features that help to search OST files from even local drive.
It provides safer and faster OST to PST conversion.
The user can split a PST file by Size, Date, and Folder. The tool offers to split the PST file in various sizes between 1GB to 10GB while preserving the original organization of the mailbox data.
More info:- Free ost convert to pst