I have a survival world I have been playing on it before I got the dinosaur mod. Can I get the fossils to spawn in caves on this world? Or do I have to make a new world in order for the fossils to spawn in caves and other world generation? I'm having the same issue with the dragons mounts mod.
You can still use your existing maps, but you'll have to go for some exploring.
Under normal circumstances with any pre-existing map, you would have to explore your map particularly further in order to find chunks that you have not yet discovered in your map. If you start to generate new chunks in your map, they may hold some of the ores that come with the mod.