How can I retrieve my deleted old videos

Once deleted, photos and videos go to a deleted folder in the Photo app for 30 days to give you the opportunity to restore them. After 30 days, they are PERMANENTLY deleted, which means there is no place to restore them from. Unless of course you wisely backed them up somewhere, where they could be restored from. If you didn't do that, they're gone.

That would be from a backup that was created before they were deleted. Did you save them in another location or create an archived backup using a computer before they were deleted? When deleted from your device, they will only remain in the Recently Deleted album for 30 days unless deleted from there before that time.

If they are not in the “Recently Deleted” folder in Photos, they’re gone.

Perhaps you housed them somewhere else where they still exist, such as a computer or camera’s SD card.