would know it
Si hubiese ganado un viaje, lo sabría.
If I had won a trip, I would know.
— El quinto elemento (1997)
I would know.
Si alguien estaba escuchando, lo sabría todo.
If someone was listening, they would know everything.
— Uno de los nuestros (1990)
Si Tom estuviera en problemas, Mary lo sabría.
If Tom was in trouble, Mary would know.