You can see below all the manual procedure for converting OST files to PST file format.
#1 Import and Export
#2 Drag and Drop
Now follow the methods in detailed to Convert OST to PST file manually:
There is a word limitation for answers so couldn’t jot down the whole manual process.
As this site isn’t allowing me to do that.
SO I would suggest you to check out this EasyTechTools BLOG for detailed manual procedures.
How To Convert OST Files To PST