i restored my ipad air and in final steps it says press home to upgrade. my home button is broken. what should i do?

You should make an appointment at the nearest Apple Store for an evaluation and explanation of your options. Obviously you must get Home button fixed.

You will need to get your iPad replaced. There is no substitute for a broken home button. Schedule an appointment at your Apple Store Genius Bar for options.

Assistive touch won't help you here. You need a functioning home button.