Hi. All of above are correct in tense and usage as explained, but there is caveat. When you are asking, "How do you say ____?" and you are asking for a translation of a word or phrase from another language, like English (i.e. the word car), it is often more common (and appropriate) to ask ¿Qué quiere decir *car* en Español? ¿Cómo se dice? is more commonly used when the speaker is continuing to speak spanish while attempting to desscribe the word they don't know or can't think of. I know it's minute and somewhat confusing, but nevertheless I think it's important to point out that there is a difference. Feel free to contact me with any more questions you may have. Hope I've helped.