my iphone 5c get an unknown error(1).how to fix it?

See this support document regarding update errors, Get help with iOS update and restore errors - Apple Support however, generally an error 1 is a hardware error, and you may have to make an appointment at the Genius Bar of the nearest Apple Store or Authorized Apple Service provider.

Check for hardware issues

Related errors: 1, 3, 11, 12, 13, 14, 16, 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 1002, 1004, 1011, 1012, 1014, 1667, or 1669.

These errors mean that your device or computer might have a hardware issue that stops the update or restore from completing.

1. Check that your security software and settings aren't blocking your device from communicating with the Apple update server.
2. Then try to restore your iOS device two more times while connected with a cable, computer, and network you know are good.
3. Make sure that your security software and settings are allowing communication between your device and update servers.
4. If you still see the error message when you update or restore, contact Apple support.