If you are still looking for the best OST to PST Converter Tool, then you can check out top 8 best OST to PST Converter software here.
Or you can can go with the Microsoft Forum https://powerusers.microsoft.com/t5/General/Best-Method-to-Convert-OST-File-to-Outlook-PST/td-p/2367582 to know the best method to convert OST file to PST for Outlook.
Also, I would like to suggest using Yota OST to PST Converter which I tried last week and its worked great for me.