How to Recover My iPhone Contacts on My Computer
Losing the contacts on your iPhone can be frustrating, especially if you do not have important numbers committed to memory. Fortunately, you can recover your lost contacts by restoring a backup of your device's data using iTunes. The iTunes application automatically creates a backup of your data when you sync your iPhone with your computer. Therefore, regardless of the reason your contacts were deleted, you can use iTunes on your computer to restore your contacts from the backup of your last sync.
Connect your iPhone to the computer using its USB cable.
Launch iTunes if it does not automatically open.
Right-click on the iPhone icon under "Devices" in the left column of the window.
Select "Restore From Backup" on the pop-up list.
Select a backup from the list of available backups, and then click "Restore." The restoration process starts. Leave your iPhone connected until the process is complete. When the process is complete, your contacts will be restored to "Contacts" in your iPhone.