If you need to convert your OST file to PST then you can use a manual method to switch the Offline OST file to Outlook PST but as per my perception, You should try this third-party OST to PST Converter for Mac that can easily convert OST file to PST without having any hassle. It can transform all the multiple OST files and folders to PST in one go without any data loss. It let the users save the switched OST file to PST file format. Its GUI is very simple and user friendly. Technical or non-technical both can easily use this software without having any technical skill. This software supports all Mac OS versions and MS Outlook versions. Use its free trial version to check the features and functions of OST to PST Converter for Mac Tool.

For more info visit here:- https://www.mailvita.com/ost-to-pst-converter-for-mac/