Which report helps you understand which kinds of mobile devices were used to visit your website?
Technology > Network report
All Traffic > Source/Medium report
Mobile > Devices report
Site Content > Landing Page report
With this (Mobile > Devices report) report, you can find out how many users you acquired on one type of device convert on that same type of device, how many convert on a different type of device, and how many don’t convert at all.
Read more here: https://support.google.com/analytics/answer/3123672