Yes, you can use ost to pst converter tool to move on with the free ost to pst conversion.
Use SysInspire as an ost to pst converter to convert the ost file data to Outlook including all the contents like the emails, calendar, contacts and other items accessible through Outlook.
Conversion from OST to PST file can be done automatically and can be backed up in the PST format.
SysInspire free ost to pst converter tool converts ost files created with any version of Outlook.
Also, using this software to convert OST data to PST, one can convert offline Outlook files of any size successfully to PST file format.
After successful completion of the scanning process, the OST to PST Converter provides an instant preview Offline OST items with Preview Modes
More info:- Convert OST to PST