If you have a container with a spout on the side and a measuring device for liquid like a graduated cylinder you can fill it up to the edge of the spout and then submerge the object in water and the water that’s displaced will give you the volume of the object. If it floats you’ll have to push it down so it’s just below the surface of the water.

The conversion of mL to cm^3 is 1:1. 1 mL = 1 cm^3.

cross sectional area, pi r squared multiplied by the height, h.

V = pi r^2 h cm^3. And please do not be abusive about your teacher in future. If you do wish to be abusive, then at least spell it correctly.

the final measurement will be cubic units (cm or meters or inches)

example a cube of 3cm sides, will be 27 (3cm*3cm*3cm) cm3

if its any other shape like a rectagle maybe, (3in*6in*2in) = 36 in3

make sure the measures are the same, either all CM or all Inches or all feet. if they are not the same, you cant multiply them until you get convert them all to the same unit

but actually, it depends on the kind of solid.. there’s a different formula for a cylinder, sphere and pyramid…