"Si hoc credis, quicquam credes" might fit the bill. Literally, word by word, that means "If this you believe, anything you will believe." (Remember, Latin grammar and word order are not the same as English.)
However, I always advise anyone who seeks advice on Latin translations here to treat any answer - including mine! - with caution. My suggestion is that you ask the Classics teacher at your local secondary school, if it has such a being, or a Catholic priest.
If someone suggests an online translation site, I'd treat that with even more care. They are generally utterly useless, unless you are very knowledgeable about the language in any case.