How do I restore software for iphone 7 whose software have been erased?

Here's a help article from Apple Support for your issue: If you see error 9, 4005, 4013, or 4014 when you restore your iOS device - Apple Support

Hello Saidah

First as always:

1. Use the latest version of iTunes

2. Make sure iPhone has enough space to bring in a new update. A gig or more is recommended.

3. Make sure iPhone has enough battery for Restore (40% or more)

4. Update your Mac or PC (If there is)

And what about rebooting your iPhone? (For Rebooting You should hold Home and Power bottom until the Phone gets reboot)

And also reset your iPhone:

(Settings → General → Reset →Reset All Settings.)