The average density of whole milk is 1.034 g cm ^3. What is it's density in lb gal ^-1?

You will need to look up some conversions of gram to lbs

1 gram = 0.00220462262 pounds

1 mL = 0.000264172052 US gallons

and mL to gal

1.035 g / cm^3 x 0.0022 lbs / 1 gram x 1 mL / 0.000264 gal