"It is a place from which you cannot return."
Translation:É um lugar do qual você não pode voltar.
Because it is related to the word "lugar" (masculine word). So it matches to gender and number (do qual, da qual, dos quais, das quais)
I left the Voce out of my sentence and it was marked wrong even though it's one of the options for the correct sentence. Do you need to include voce?
can "de onde" be used in portuguese in constructions like this, as it sometimes is in spanish? ex - "de donde eres"
In this sentence, using de onde would make the sentence seems so poor... "do qual" sounds much better!!. For simple context, where there is no relative clauses or when "where" is mandatory, using "(de) onde" is perfectly correct. Similarly to Spanish we say: "De onde você é?"