If you are moving from Outlook OST to PST then you should export OST files into PST files and you have to choose the best tool, I might want to recommend eSoftTools OST to PST converter which is planned with a wonderful component like you can part your overwhelming PST files into little PST files, it supports all the refreshed form of MS Outlook from 2000, 2003, 2007, 2010, 2013 up to 2016, and interestingly, you will be permitted to export OST to PST and many formats such as EML, EMLX, MSG, MBOX, HTML, CSV, vCal.
Get More Details- Export OST files into PST
You can merge OST and PST files by using the third-party tool. ... OST Merger has the capability to combine entire data items saved in Outlook data files such as contacts, notes, email messages, etc. Then, you can merge multiple OST files into a single file with minimum effort and time.