Look in the Apple Store for the correct cable.
Why can't you use the same cable you have for the iPhone?
Does it not work?
This cable works for almost all the mobile devices to date which includes your iPhone.
What cable do you have?
A non Apple cable?
You could also use an Apple TV for this purpose if you have a newer iPad.
Which version of iPad do you have?
Apple made this confusing.
They called the 3rd generation the "New iPad".
So, do you have the now newer 4th generation iPad with the Lightning connector instead of the 30 pin connector?
If so, the 30 pin connector will not work with the 4th generation iPad.
Rather then purchasing a $40 cable that will only work on some models and not others, how about the Apple TV ?
It works on almost all mobile devices and will continue to work on all newer mobile devices. (unless Apple wants to confuse us again in the future)