hi its been a while since i have had any thing harder than plain old adding up to , so wonder if somebody could point me in the right direction

if i Have an aero bar with 0.04mm square and .1mm deep with 16 bubbles in each square , how do i calculate how many bubbles in 1mm cube

i did it my way and it made sense to me , then the kids came home and really confused me with different solutions , making me feel really thick , so if anyone knows the right way please enlighten me

thanks in advance