I’m trying to figure out how to rotate my model to always face away from the chase camera, from what I understand the camera direction is a vector and a rotation is a matrix…

Seeing as my math skills aren’t so hot.

I’m unsure how to take the Camera direction and convert it to the rotation of the model.

Would there be something to do with chase camera to make this easy?

Then you want something like:
float angle = cam.getRotation().toAngles(null)[1];
Quaternion rotation = new Quaternion().fromAngles(0, angle, 0);

I’m typing that from the top of my head but it’s something like that. You may want to cycle through some of the docs like the jme3 Math for Dummies link and the other links nearby in the right sidebar of this page. There are some good primers in there.