The personal site collection have path "https://tenant-my.sharepoint.com/".
You can use below REST API query to get a list of all personal sites.
For ex- "personalsite-my.sharepoint.com" is my site collection.In order to get list of all personal sites you can use query -
You may be comfortable writing REST API calls to achieve this. Alternatively, I would highly recommend using the SharePoint 2013 Search tool to help out.