edit: wasn't supposed to post that question
Volume of a Frustum of a Cone
gives the volume as where "r" and "R" are the radii of the two bases and h is the vertical height of the cone.
Once you have that, you will need to estimate the volume of a single jellybean and divide one volume by the other.
and you'll need to account for the volume lost in the space BETWEEN the jelly beansOnce you have that, you will need to estimate the volume of a single jellybean
If the picture shows some jelly beans, then scale the size of a jelly bean. You may need to scale the length & width of a dozen or more to have a reasonable "average" size jelly bean.and divide one volume by the other.
Use that scaled jelly bean to determine the diameter of the top and bottom radius and height of the frustrum & then make your calculations.
You may want to buy a bag of jelly beans, measure a cup full and then count them.
THEN (this is the fun part) mash/smash/pulverise/compress as many jelly beans as possible into the cup.
(YOU NEED TO COUNT THEM BEFORE YOU SQUEEZE'M)
With that you can account for the lost space between the beans, and thus estimate somewhat more acccurately than just a WAG.