Two graduated cylinders, one filled with water to 20 millimeters and one containing a rock and water filled to 32 millimeters. Use the image to determine the volume of the rock. Initial volume: mL Final volume: mL Volume of rock: cm3

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!