Add all Contacts to this device
How to add complete list of Contacts to another iPhone that matches the Contact list in my Mac.
Diana"s iPhone
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With iCloud enabled and with your systems all logged into the same Apple ID, Contacts synchronization can be enabled.
If your iCloud Contacts, Calendars, or Reminders won’t sync - Apple Support
If you don’t want to use iCloud, you’ll want to find a CardDAV server and (re)locate your contact information there.