First find the volume of the rectangle prism. Do this by multiplying all three dimensions. 412 x 412 x 6 = 1,018,464.
Subtract 1,018,464 from 143.
You should get 1,018,321 mm^3
(Remember that the units are cubed because you multipled 412 mm x 412 mm x 6 mm which is multiplying not only the numbers, but the mm three times as well.)