Error 3 is related hardware issues that can be from device or computer, so you need to check both computer and your iPhonoe. Hope the following tips are of help:
1. Check that your security software and settings aren’t preventing 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. Confirm that your security software and settings are allowing communication between your device and update servers.