Need help. My car was placed in storage and both batteries disconnected.

I anticipate both batteries to be dead.

Can someone provide instructions on best way to go forward / will these batteries be salvageable to recharge or should I replace ... are they under warranty.

Will the dealership warranty the battery?
What will be the fault codes ... again I anticipate the car will have to be reset by the dealership.

When I travel for over 90 days in the future ... what is the best method to store the car???

thanks for the help!!!!