How to Get Quaternion from 6-Axis Serial IMU

Dear all member and experts,

I am using Serial 6-Axis Accelerometer Module from DFRobot. This sensor outputs Accelerometer, Gyroscope, and Angles data only. I need Quaternion data to make rotation matrix. Then, I put them into homogeneous transformation matrix. How to get quaternion data from these data? or Is there any library that processing quaternion from IMU?

Best regards and thanks,

Octarudin