They are all correct, but they mean different things. Sentence one in the second conditional form, it is about a hypothetical situation. Sentence two is in a mixed conditional form. It involves something that did not hoped in the past and something that is untrue now. Sentence three is in the third conditional. This concerns something threat did not happen and the past, and a result that did not occur in the past.

1. “If you told me that, I would remember.” This is a mixed tense sentence. It's used when you're unsure if something happened, but you're pretty sure it didn’t. Used when: You’re imagining a past situation in the present. Example: "Are you sure you told me that? Because if you told me that, I would remember." (You're saying: I don’t think you did, because I don’t remember it.) This is grammatically correct and natural in speech. 2. “If you had told me that, I would remember.” This is a grammatical mismatch — mixing past perfect and present. It's not standard in formal writing, but it can occur in casual speech. In formal English, this isn’t correct. In casual speech, people sometimes use it, meaning the same as sentence 1. 3. “If you had told me that, I would have remembered.” This is the fully correct form for talking about a past situation that didn’t happen. Used when: You're clearly talking about a past moment and a past reaction. Example: "If you had told me that yesterday, I would have remembered today." This is 100% correct and most appropriate for past situations.

David L gave an excellent answer.

I would say they're all acceptable. But I also expect the average examiner to say the first and last sentences are okay and the second is wrong.

Your number 3 is correct.