Help please? Downloaded ubuntu 13.10 onto usb and can't find .iso file in order to create a bootable usb

Help please? Downloaded ubuntu 13.10 onto usb and can't find .iso file in
order to create a bootable usb

I asked a question which was immediately merged with this question: How do
I install Ubuntu from an USB drive / create a live USB-stick? .
I can understand most of what is said there, except that when I try and
use http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/ to
create a bootable usb (i want to create one with a laptop which has no cd
drive so i can install in on my pc with new blank harddrive), I can't find
the .iso file. I downloaded ubuntu 13.10 desktop onto my usb and extracted
all the files. So when I am on that universal usb installer i am browsing
for .iso files among the ubuntu 13.10 files i downloaded but just can't
find one!
To be honest I am a beginner and barely know what a .iso file is so please
bear with me, be amused and help me not go back to windows!