Transfer Data from iPhone to iPhone 6/6s (Plus) via iTunes:
Step 1. Make a backup for your old iPhone via iTunes.
Step 2. You should turn off your old iPhone because it’ll cause conflicts with backups in iCloud.
Step 3. Turn on your new iPhone to set up your iPhone and tap on Restore from iTunes Backup.
Step 4. Connect your new iPhone to iTunes on the computer, which you used to backup your old iPhone.
Step 5. iTunes will ask you to restore from backup or set up as new. Select the latest backup of your old device and click Continue button. Make sure that iTunes is showing you the latest backup of your old iPhone.
Step 6. When the restore process is complete, your new iPhone will restart. Then it will be ready for use.