If you want to migrate your Yahoo mails to PST format, I recommend using the Aryson Yahoo Backup Software. It is one of the fastest solutions for creating Yahoo backups on the internet. You can use this software to migrate your Yahoo mails to PST and other file formats like MBOX, MSG, HTML, EML, EMLX, and MHTML. You can check out its demo version, which allows converting the first 50 emails for free.