How do u block robocalls on iPad like u can on ur iPhone

See >>> Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch - Apple Support

Your blocked contacts list synchronises between your iPhone and iPad via iCloud. As such, assuming that you are signed in to iCloud with the same AppleID, the same block-list will be present on both devices; adding an entry on one device, adds the same entry to all devices that are signed-in to iCloud with the same AppleID.