You can't recover the original owners apps and data. His purchased content is tied to his Apple ID and that content belongs to him. That is why he erased the iPad.
Set it up as a new device, get your own Apple ID if you do not have one and start downloading your own content or sync any purchased content from iTunes if you have another iDevice.
What do you mean about "you need to recover the software"? What software? The iOS is already on the device.