If you had known me, certainly you would also have known my Father. And from now on, you shall know him, and you have seen him.
Other versions
King James Version
If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him.English Standard Version
If you had known me, you would have known my Father also. From now on you do know him and have seen him."New International Version
If you really knew me, you would know my Father as well. From now on, you do know him and have seen him."