The best program for recovering OST file data and converting OST files is SysInspire OST to PST Converter. This program can also open and view OST files. OST can be converted to PST, EML, EMLX, Yahoo, Gmail, Zimbra, HTML, MSG, vCard, and more formats. From damaged or corrupted OST files, it also restores all addresses, conversations, attachments, contacts, notes, papers, and a range of other information. SysInspire also provides a free trial version.
Read More:- Convert OST File to PST

I would recommend you to use the OST Exporter tool to convert the OST files into PST file format This tool is the most reliable and intuitive utility to use. It converts the OST files into PST, EML, EMLX, MBOX, MSG, and VCF formats. With this OST Exporter tool every users can simply convert OST into PST and several more formats in simple clicks. You can also download its free trial version to converts 10 iteam each folder. Visit here for more info: https://www.betavare.com/ost/
How to convert an OST to a PST file
Install Recovery Toolbox for Outlook in Windows.
Start Recovery Toolbox for Outlook.
Select an OST file on the first page of the program.
Select the Converter mode mode.
View the content of the OST file.
Select a folder for saving converted data.
Select the Save as PST file mode.
Click Save.
Regards,
Willjoe