hello trishladish, due to apple's restrictive policies it is unfortunately not possible to implement & offer independent third-party browsers for idevices.
mozilla is prohibited to bring the rendering & javascript engine of firefox onto iOS, since apple is only allowing the use of its own webkit in the terms & conditions for developers - as long as this is the case, firefox and its addon ecosystem cannot be ported to iOS devices.

http://www.pcmag.com/article2/0,2817,2416461,00.asp

What were you trying to download as the Mac version from mozilla.org is for the OSX.

If not for the Apple restrictions Mozilla would likely have had a mobile version of Firefox like they do for Android 2.2+. They did have a browser experiment for iOS back in 2012 called Junior though it was never released to public. It did not use the Gecko engine that Firefox and SeaMonkey uses.