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.
https://<site_name>.sharepoint.com/_api/search/query?querytext='contentclass:STS_Site Path:"https://<site_name>-my.sharepoint.com"'
For ex- "personalsite-my.sharepoint.com" is my site collection.In order to get list of all personal sites you can use query -
http://personalsite.sharepoint.com/_api/search/query?querytext='Path:"https://personalsite-my.sharepoint.com contentclass:STS_Site"'
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.