What was the total weight (lbf) of chocolate in the vat? the specific gravity of chocolate is approximately 1.24?

I believe this question is missing some information, but I'll just tell you how to solve it and you can apply using the information you have.

First, we have the specific gravity which is the ratio between the density of the substance to the density of water at 4 degrees celcius (1000 kg/m^3)
specific gravity of milk = density of milk/density of water
1.24 = density of milk/1000
density of milk = 1240 kg/m^3

Then we have:
density = mass/volume
I believe the question should have any information regarding the volume.
You will use this information to calculate the mass of milk in kg.

Then, you will change the kg to pound (lb) using cross multiplication. 
(1 kg = 2.2 lb).

The last step is to calculate the weight in lbf. To do this, you will simply multiply the mass (in lb) by the gravity (9.8 m/s^2)