The correct option is C Would have gone
The type 3 conditional is used to refer to a time that is in the past, and a situation that is contrary to reality. The facts they are based on are the opposite of what is expressed. The type 3 conditional is used to refer to an unreal past condition and its probable past result. In type 3 conditional sentences, the if clause uses the past perfect (if I had known his address), and the main clause uses the perfect conditional (I would have gone to see him). Hence, Option C is correct. The rest of the options do not express this conditional, hence they're incorrect.