How do download camera?

There is no way to download the camera App, nor is there any way to delete the camera App. Check: Settings - General - Restrictions - Camera = ???

It's part of the iOS and cannot be deleted or downloaded. I'm assuming you can't find it on your iPad...

Search all home screens and all folders.

Also check Settings > General > Restrictions to see if it has been restricted.

If not found, Settings > General > Reset > Reset Home Screen Layout.

Which iPad model do you have? Please note the first generation does not have a camera.

Also note it is much easier to help you if you stay within the same discussion instead of starting a new one.