There are many tool in the market but In my Opinion I want to suggest you this OST to PST Converter Software that can easily Convert single and multiple OST files and Convert them into Outlook PST format without any risk of data loss. if you have Corrupt OST file then don't worry this Software also Repair your Corrupted OST file and Recover your deleted OST file data with all attachments. you can also save 30 emails per folder at free of cost by using this Software free trial version.
if you are facing problems in migrating OST to PST file format I will recommend this OST to PST Converter tool this tool is very effective and easy to work you should give this tool a try you can download the software from here:-