There is no Firefox for the iPad. No program you download from the internet will work on the iPad. Only apps you get from the App Store will work (or Cydia if you jailbreak) and there are plenty of apps to choose from.
As SweetPoison so gently pointed out, there are several alternate browsers for the iPad. If you are dissatisfied with how Safari works a search will turn up many threads where people discuss their favorite browser, so if SweetPoison's link does not satisfy, dig into some of them.