Here you get a variety of overviews in regards to apps. In all of these reports you can click on an entry to further see which versions are installed on the devices and how often. In this view you can click on a specific version again to see which devices have this specific version installed.

Note: It may take some time until the system gets an up to date information from the device. Additionally the reports are not updated every minute. You might need to be patient to see the current status if you just have assigned a new app or version. Manually reloading the report will force the report to show the most up to date data available