Typical Baptistt/Evangelical (Graham is a Baptist) theology says that our sins have been forgiven, but we must accept this forgiveness (by accepting Jesus as our “personal Lord and Savior,” usually by saying a “sinner’s prayer”). This is the one event that “saves” you (the first two letters of OSAS).
It is unlikely that Hitler was ever “saved” in the protestant sense, so they would say that Hitler could not be in heaven.
FWIW, it is likely that Hitler underwent Christian Baptism as an infant, so it is possible (from a Catholic viewpoint) that he could be in heaven. I would rate his chances pretty low, but we can never say for sure.