Open the Google Maps
page and put this in for a search:
In der Raste 1, 53129, Bonn, Germany
It will show you the hostel; there is even Street View (entrance is on the Dottendorfer Straße side), but of course it is nothing much to look at from the outside!
This appears to be a few blocks off the west bank of the Rhine in the south side of Bonn... presumably not a place where it would be easy to find a campground for your own (or rented) caravan.