How can I consolidate all Apple devices and data under one account (including late wife's)

I have multiple old and new Apple devices. I somehow have got 2 AppleIDs (accounts, I guess). My late wife also had a phone and iPad. I'd like to have her (new-ish) iPad registered under my name (I can already access it since she gave me her pin). I'd ALSO like to keep her digital legacy (ALL her data from old and new devices) and consolidate that data and mine on one iCloud account.

(I'd rather have someone do this for me than stumble through it myself, even if I have to pay for that support.)

At present ONLY my late wife's iPad is under Applecare.