The OST to PST blog that I share is very well-written and informative. This blog assists me in converting OST files and thoroughly explains the methods provided. Check out this helpful blog. You can get a good result using these free methods.
Convert OST to PST Manually
Open Outlook and go to the File menu.
Select the Import/Export option.
Choose Export to a file.
Select Outlook Data File (.pst)
Choose whether to export a specific folder or the whole account.
Check the Include subfolders box.
Next, select a destination for the Export, and then click Finish.