#### Answer

$3.06 \times 10^{-3}\ ft^3$

#### Work Step by Step

Remember that when there is a squared term or cubed term in the units, we need to adjust for that. For example, it we are converting from $mm^2$ to $m^2$, we need to multiply by $10^{-6},$ not $10^{-3}$. Using this and our knowledge of units, we find:
$87.3 \times 3.5 \times 10^{-5} \ ft^3$
To convert to scientific notation, move the decimal to the right or left, counting the number of times that you do so, until you get a number that is at least 1 but that is less than 10. If you moved the decimal right, the number of times the decimal is moved will be negative, while moving left yields a positive number. Then, raise 10 to that number. This gives:
$3.06 \times 10^{-3}\ ft^3$