As simple and sure as this...
Acts 16:31 Douay-Rheims 1899 American Edition (DRA)
31 But they said: Believe in the Lord Jesus, and thou shalt be saved, and thy house.
Romans 10:9-10 Douay-Rheims 1899 American Edition (DRA)
9 For if thou confess with thy mouth the Lord Jesus, and believe in thy heart that God hath raised him up from the dead, thou shalt be saved.
10 For, with the heart, we believe unto justice; but, with the mouth, confession is made unto salvation.
That’s true.