i have an iphone 6 with broken home button which says press home button to upgrade

It’s going to have to be fixed, or Apple is going to have to use some internal and non-standard mechanisms to offload the contents of the iPhone should you want to preserve and migrate those contents over to a replacement iPhone.

Get an appointment at an Apple Store for an evaluation and get it fixed.

Use this to find out who does service in your country. Contact Apple for support and service - Apple Support

Will Assistive Touch work?

https://support.apple.com/en-us/HT202658

https://gadgets.ndtv.com/apps/features/how-to-add-touch-screen-home-button-on-iphone-ipad-648588