If you wish to recover email from OST to Outlook 2016, then thinking of manual methods is just like doing an overburdened work.
You should always prefer third-party tools for the conversion just like me.
I will recommend you to use the SysInspire OST to PST converter that will recover the emails from the OST file and get it transferred to Outlook 2016.
Not only 2016, but other outlook versions can also be favoured like 2007, 2003 and the lower versions.
You may have the older version but the software is so well promulgated that it can recover the files from the oldest version eve.
Download SysInspire OST to PST software.
Click Find OST File option to locate the OST file.
Click Browse to select the location to save the converted file.
Click the Convert option to start.
This will smoothly recover the email from OST file Outlook 2016.
More info:- Recover email from ost file outlook 2016