Cadry Ruins is an intermediate grind-zone. Cadry mobs are primarily fought for quest-related reasons and also used as a grind spot early on. The xp here is decent but nothing special. With that being said, this spot is decent early on, but you should focus on questing until you reach level 56 - once level 56, you can grind Polly's for better, more profitable rewards. Polly's is also one of the best spots in the game for xp. If you reach level 56 but still cant kill pollys Cadry mobs will do until then.
Cadry Ruinds is located east of Altinova; Altinova is Black Desert's fourth major city when you start the game.