Open the Contacts app on the source iPhone
Make sure the contacts are synced to iCloud
On the new iPhone, sign in with the same Apple ID
Turn on Contacts in iCloud settings
Wait for the contacts to sync automatically
If needed, use AirDrop to share individual contacts
If needed, use a SIM card to import contacts
If needed, restore the new iPhone from an iCloud backup
If needed, use Finder or iTunes to transfer a backup to the new iPhone