Need to sync with a new computer without loss of data etc.

I am a victim of the Sonoma CA fires in October 2017. I still have an ipad, a laptop and an iPhone that are synced to the computers that burned up. How do I sync with my new computer without loss of apps, data, etc.? And two, I noticed that the new ITunes does not show any categories for apps, etc. How do I get that to work?