To find out how many pounds of flour Eric should use for 1 cup of sugar, we need to determine the ratio of flour to sugar.
In the recipe, it says that there are 2 1/2 pounds of flour for every 1/4 cup of sugar.
Let's convert 1 cup into 1/4 cup: 1 cup = 4 * 1/4 cup = 4 * 0.25 cup = 1 cup
Next, we can use this ratio to determine how many pounds of flour Eric should use for 1 cup of sugar.
Since there are 1/4 cup of sugar required for 2 1/2 pounds of flour, we can calculate how many pounds of flour are needed for 1 cup of sugar by multiplying the number of pounds of flour by 4.
So, Eric should use 2 1/2 pounds * 4 = <<2.5*4=10>>10 pounds of flour for 1 cup of sugar. Answer: \boxed{10}.