「ください」を使うなら、「私の翻訳を手伝ってください。」となります。
英語と同じ疑問文で「手伝ってくれませんか？」か「手伝ってもらえませんか？」と訳すのが、よりふさわしいでしょう。

@CK,

I have some hesitations in adding alternate translations.
For example, I can translate your sentence "Please translate this for me?" as "これを訳してくれませんか？". "これ" can be "この文章" (not a literal translation, but sounds more natural), "訳" can be "翻訳", and "くれませんか？" can be "くれますか？", "くれないでしょうか？", "もらえますか？", "もらえませんか？", "もらえないでしょうか？", "いただけますか？", "いただけませんか？", "いただけないでしょうか？", "くださいますか？", "くださいませんか？", "くださらないでしょうか？" and so on and so on, and all the combinations are almost equally appropriate. In a case like this, I've preferred to choose just one version, unless there are several ways to say that use radically different structures.

I have another problem with this sentence. If I saw the sentence ("Please translate this for me?") alone, then I'd translate it without "私のために". Of course you could say "私のためにこれを訳してくれませんか？", but I think we say "私のために" in Japanese much less often than you use "for me" in English. If I see the sentence side by side with another one "Please translate this?", however, I'm tempted to add "私のために" to the former one in order to differentiate them, though I do think that the sentence with "for me" must have a translation without "私のために", too.

What am I supposed to do in this kind of case?