Unfortunately, accurately converting pound measurements to cup measurements is impossible without knowing the exact substance in question along with its weight and density. This is because a pound is a weight measurement whereas a cup is a volume measurement.
However, if the substance is known, one can find an online calculator that will help figure out how many cups of something equals a pound and vice versa. For example, a cup of Reese's Pieces candy weighs approximately 0.415 pound according to the weight to volume cooking converter found at Online Conversion. One can also covert manually to know the density of the substance.