Free tool to convert OST files to PST format are not that much reliable applications as they are not complete versions of that software. They also don't give a complete conversion of OST file. The better option to convert is either a paid tool like Softaken OST to PST Converter.
Sotknoll OST to PST Recovery Software gives the best result for recovering OST emails into MS Outlook 2016(PST). With the help of this solution you can recover OST emails according to your required such as:-“from date” to “end date” along with all OST file aliments and properties.
There is one more solution to convert OST file to PST format. This tool will recover corrupted OST file and export into PST, EML, MSG and MBOX format. For more details please visit Softknoll.com