If you have contacts in you CSV files and want to convert them into vCard format as it support in multiple email client and smartphone too. You can make use of GainTools Address Book Manager. This tool can migrate from CSV format to VCF format safely on any Windows system. Refer: https://www.gaintools.com/address-book-manager/

The effective way to convert OST files into Outlook PST file format is using a software through which you will get outstanding results. Users can make use of GainTools OST to PST Converter for effortless conversion of OST to PST format. This application allows your to make the task done in a few clicks without any alteration in email data. For full guidance you can read this blog: https://www.gaintools.com/blog/convert-ost-to-pst-know-about-professional-solution/