How to transfer contacts from one iPhone to another

If you turn on iCloud, you get 5 GB of free iCloud storage. Information such as contacts, calendars, bookmarks, notes, reminders, voice memos are stored in iCloud.

You must use the same Apple ID.

FYI: Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.

You can’t merge multiple Apple ID accounts.