Let me put this plain and simple: WhatsApp is an iPhone tweak that is $.99 (USD) at the App Store. It is NOT free.
Jail breaking, while allowing you to install WhatsApp on your iPad (with a bit more fiddling than you'd think) - is NOT going to get that app for you for free. To get a paid app for free is called piracy, which theft, which is illegal. In addition, piracy, and any discussion thereof is against this forum's rules.
Bottom line - WhatsApp is an iPhone app that costs money. It can be bought and put on a jail broken iPad (again, with a bit of work).
Marilyn