Jennifer, I am sorry for your loss. You will need at least one copy of the official death certificate in most cases to see and have access to the assets.
Which benefits? Social Security has a website and you can view what they expect to pay and when.
If you are looking at benefits from his employer, you would need to contact them.
I can help more and personalize the answer over the phone 6770-954-8823 or email. Best Wishes, Stephanie