Forgot my safe combtion

If it's a sentry safe.."For you and your safe's security, you'll need a Notarized Statement of Ownership. The statement of ownership did not come with your safe and is an added security measure. The statement is an official document that proves you own the safe and is notarized by a licensed Notary." ..deal with Sentry for this procedure.
If it's a brand name gun safe etc, .purchased through a lock shop..likely only the original combination may be recorded..nothing if you've changed it since then.
some safe's have a code label..that can be used to get the combination from the manufacturer once you prove ownership.
if there are extreme valuables inside it can be opened by a safe specialist and/or locksmith.