Which case do I need here?

Which case do I need here?
Dative preposition
1. Is there a preposition? If so, is it a ...
2-way preposition
Accusative preposition
2. Is the verb “sein” = to be?
3. Think
a) What is the verb?
b) Who/what is doing the verb?
c) The subject is “verbing” what?
d) The receiver
Nominative
Subject
Dir. object
Nom.
Acc.
Indir. object
Dat.