The free tool you’re looking for is Itunes, that’s if you backed up your unit. The other feature that helps is your Apple ID, which is linked to the cloud services that give you 5 GB for free. This should have some of your content unless you unsync’d it.
Other options are to pay services that allow them to pull out what they can, most of which are achievable.
As for Whatsapp, the app has it’s own cloud base to store information. When you log back in using the same credentials it should all come back, UNLESS you undid it in the settings.