iPad 2017 unable to restore/update
Download the restore image for your model of iPad from https://ipsw.me. You should be able to get the restore image for iOS 12.3.1 (current as of this writing).

Once you have the image, connect the iPad to your Windows PC, launch iTunes, and press and hold Shift key and click on the Update button. You'll be prompted to select a restore image. Point to the downloaded image. This should do away with the network error 3259 that you are getting.

Your iPad would be set up from blank state. You'll have an option to restore from an iCloud backup directly over-the-air.