IMU Implementation onto Simulink

I am trying to implement an IMU sensor with an accelerometer, gyroscope, and magnetometer on Simulink. I am creating this model with generated data not real data from an IMU for the purpose of algorithm verification.

I am trying to take the nine inputs (x,y,z of each sensor) and, apply an inverse rotation matrix to obtain the values in a different reference frame.

I am struggling to understand how I am to apply quaternions to obtain pitch, yaw, and roll in theory. How am I supposed to convert the nine inputs into quaternions?

Attached you will find a visual representation of my algorithm.

IMU ALGORITHM

Thanks