Can I cash in a fully paid insurance policy that my decesed grand father had on me

You would keep paying the premiums after his death. Are you sure it hasn't expired? Have you called the company?

Well I called them and they said I would have give them his birht date and ssn# for a manual search to get the policy# but my question is do I have rights to the policy he had on me. And if it's expried is it anything I can do are is it a lost cause.

If a policy is a fully paid, that is a term used for a life policy that is paid up ( no preimums due any longer)

So do you know what type of policy it really is,

Next who was the owner of the policy, and what are the terms of the policy if he was the owner but he dies ( the terms of the policy will specify)

So at this point you either have not told us, or don't know enough info for us to tell you if you have any rights.

If it is really a fully paid up policy, and if the terms of the policy make you the owner upon his death or at a certain age that you turn, then yes you have rights.

The cash value will of course be a lot less than the face value of the policy. A 10 or 20 thousand paid up policy may only be worth 1 or 2 thousand ( if that) if you are young.