How many candy corn pieces can fit in a one gallon container?

I will assume you are talking about 24 oz in weight (i.e. 1.5 lb). You would have to buy a small bag of candy corn to figure this out. For instance, if it is a 1.5 ounce bag, and you count 21 candies, then you would multiply 21 by 24, then divide by 1.5:

21x24/1.5 = 504/1.5 = 336 candies would weigh 24 oz.

If you are talking about fluid ounces, then fill a 1/4 cup measure with candy and count them. 1/4 cup is 2 fl oz, so multiply by 24 and divide by 2.