If you want to convert NSF to PST format, you should try an easy manual tricks. The manual trick doesn't require any third party tool or any other cost. You need to use IBM Lotus Notes here. It provides you file formats into which you can save your NSF file's data: Comma Separated Value and Structured Text. Both these file formats are supported by Outlook client. Once you save NSF file's data into any of these file formats, you can import this new file to Outlook client by using its Import feature.
Refer to this blog post for detailed information:- http://migrateemails.com/export-lotus-notes-email-to-microsoft-outlook/