Assuming that you are running the same iOS on both devices ..... Do you use iTunes? Transfer purchases from the iPhone into iTunes, backup the iPhone, and sync the phone again. Connect the iPad to iTunes, restore from the backup of the phone and then sync with iTunes.
iPhone only apps will appear in their native size on the iPad screen but they will work.
Restoring from the backup will place all of the app data, device settings and documents onto the iPad but you still have to sync with iTunes in order to place of the apps and your other media onto the device.
if you use iCloud only, restore the iPad from the backup of the phone and that will take care of everything.
Some useful and informative information here.
How to backup and restore from a backup