Right. Advice is uncountable in English and so you can't have "an advice" (you can have "a piece of advice" though). The translation I see is "I need some good advice" which is fine, perhaps "I need a piece of good advice" works too.
"Advice is uncountable" is it in Portuguese too? It seems like it is different to English.
You are right, it is different, in Portuguese it is countable, you can say "Ele me deu dois conselhos sobre filhos".
so far, it seems (according to duo) that português accepts both forms. But I've also seen cases where the phrase changes when they're placed differently