How to make any dice have a given face(int) face up?

huh ?

I don't follow your question, but if what you're trying to do is orient the dice so that a particular face is pointing up, i'd suggest 1) attaching a transform (game object) to each face, with the positive Z direction facing away from the die. 2) choose which face you want to orient up. 3) get that face's transform's Z direction. 4) use Quaternion.FromRotation() to get the rotation need to rotate that Z vector to world Up. 5) apply that rotation gradually with Quaternion.Slerp() to get a nice animation.