Open the Contacts app on your Mac
Sign in to the same Apple ID on both iPhone and Mac
On iPhone, go to Settings
Tap your name
Tap iCloud
Turn on Contacts
On Mac, open System Settings
Click your Apple ID
Click iCloud
Turn on Contacts
Make sure both devices are connected to Wi-Fi
Wait for contacts to sync automatically
On Mac, open Contacts to confirm the sync
If needed, refresh by restarting both devices
If using Gmail or another account, add the same account on both devices and enable Contacts