I am using Kurso de Esperanto to learn Esperanto and I had to read a selection then answer questions. One question asks "Kiom da tagoj ni vojaĝis?" I want to answer with "You traveled FOR three days." So I would think to write, "Vi vojaĝis POR tri tagoj," but I don't think that's quite right because "por" means for as in purpose. So I would read my answer as "You traveled because of three days."

I also considered using "da," but then I would read it as "Vi vojaĝis DA tri tagoj," which I would translate as, "You traveled OF three days."

Please help me with this sentence.

Vi vojaĝis dum tri tagoj.

or "vi vojaĝis tri tagojn"