To transfer contacts from one iOS device (iPhone or iPad) to another:

1. Use the same apple ID on both devices.
2. Go to Settings > iCloud on device 1.  Turn on ‘Contacts’.
3. Go to Settings > iCloud on device 2.  Turn on ‘Contacts’.
4. Make sure both devices are connected to the internet.
5. Open the contacts app on device 1 and tap the ‘sync’ sign in the top left.
6. Repeat step 5 on device 2.