Looking for Kent in Gothic 3? Yes, I could not find him either and there was little help elsewhere, so I made this page after I found him.
First off an image of the cave he is in. There are four Malicious ripperbeast nearby which you must kill as part of the quest.
His location is directly north of Montera and east of Silden and Okara:
Here is a "zoomed" version of the map:
Enjoy :) If you found this helpful, please leave a comment down below!