Q: contacts missing

Did you sync them with iCloud?  Did you sync them over to your computer?

If you synced them over to your computer, then they should be on the computer, and you would simply need to sync them back to the iPhone. 

What type of computer do you have....Mac or windows?

When you have your device connect to your computer, launch iTunes, and make sure you are on the "info" tab.  There should be an option to "check off" to tell the computer to sync the data in contacts to your iPhone.  Once you check it off, click "apply" in the bottom right, then "sync" in the bottom right.