You need to get the User-Agent header. There is a GetHeader method in the HTTP Commons module you can use to get this. You can then pass this value into the 51 Degrees module to try to decode it into something a bit more useful.
Note: The HTTP Commons module may need to be loaded into Mendix 7 first, and then upgraded. The 51 Degrees module uses older freely available data so may not have the latest browsers.