Now this is eternal life: that they know you, the only true God, and Jesus Christ, whom you have sent. (NIV)

And this is eternal life: [it means] to know (to perceive, recognize, become acquainted with, and understand) You, the only true and real God, and [likewise] to know Him, Jesus [as the] Christ (the Anointed One, the Messiah), Whom You have sent. (AMP)

And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent. (KJV)