how do i recovered deleted vidoes from my i phone 6 plus

You can only do that, if there are still some videos left in the "recently deleted" album on the phone, or, if you still have a backup taken before the videos have been removed from the phone.

Photos and videos stored in the camera roll are part of the backup taken by iTunes. But, restoring from that backup will also set back all other settings to that point in time when the backup has been made.