how to transfer contacts, apps, photos etc from broken iphone 7 to iphone 6?

First of all, when an iPhone is broken, there is no way to transfer anything from it.

Normally your data would transfer from the backup you had created before the catastrophe broke your iPhone. But in this case, even that would fail, as your iPhone 6 is too old to use the current iOS version which hopefully your iPhone 7 was using when its backup was created.

If you housed your contacts and/or photos in iCloud, they will show up on your replacement iPhone once you sign in using your Apple ID. Similarly your apps (code, but not data) that you “purchased” (whether free or not) from the App Store and are still available there will be automatically downloaded to your replacement iPhone.