You can measure the volume of a rock using cubic centimeters because rocks do not have a defined shaped so you have to use water displacement to find the volume of a rock. If you had a defined shape there are different methods but for an undefined shape( rocks) you use this method.
To solve all you have to do is know how much there was in the container without the rock then how much there was with the rock. Then you take the total and subtract the original measurement you had.
