Catalyzes the oxidation of formate. formate + NAD(+) = CO2 + NADH Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Binds 1 [4Fe-4S] cluster. Dimer of an alpha and a beta subunit. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.