list of site collections created when people create with office 365 groups.

null null, I think I understand what you're asking for. I don't believe there is yet a way to view SharePoint sites borne of Office 365 Groups like you can in the SharePoint admin panel's site collection list, but I also believe I've heard that this kind of view is coming.

The next-best thing I've found is in the Admin Panel: look for Groups under Users. That shows any Office 365 groups, and that can give you an idea of how many sites are floating around.