Yahoo Backup Tool
is an outstanding utility that is well capable of converting Yahoo emails into PDF, PST, EML, EMLX, MBOX, MSG, HTML, JSON, etc. The tool backup your all Yahoo mailbox items such as emails, contacts, calendars, etc. Moreover it also offers to migrates Yahoo mailbox into Gmail, Office 365, Thunderbird, Zoho Mail, GoDaddy, etc. You can download the free demo version of this software to analyze the performance.
However, if you want to backup your emails to hard drive then you will go with this informative article Backup Hotmail Emails To Hard Drive.
Here you will get the most suitable complete manual solution to migrate the process.