This doesn't really translate well. But i think to express the same meaning it would be "how can we find him?" or "How can he be found?"
This type of Vietnamese question is quite common. Your suggestions "How can we find him?" and "How can he be found?" may be difficult to translate (does not sound natural if translating literally). I can accept them as secondary answers but not as main answer.
"How to find him?" is not a correct English sentence. I think the best translation might be "How does one find him?"
I think "How does one find him?" is a general sentence, then the absolute pronoun would be used in Vietnamese (this is not included in the course, and there are much many more pronouns):
The absolute pronoun người ta has a wider range of reference as "they, people in general, (generic) one, we, someone".
(Then, would you prefer the expression in this lesson not to be included? This expression is very simple to translate to Spanish as ¿Cómo encontrarle/encontrarlo?, and a good interpreter would translate the sentence with người ta as ¿Cómo lo/le encuentra la gente -a él-? or ¿Cómo se lo encuentra?, I think the latter is much better.)
one (used as French on) = người ta
(I hope it helps.) ;)
From Wikipedia: https://en.wikipedia.org/wiki/Vietnamese_pronouns
No question about the Vietnamese but throughout the course the English needs to be correct as well. The point that the Vietnamese can be shortened is well taken but the subject, whether "you" as N. Americans would say or "one" as Brits would say, cannot be excluded. Better to deal with this point in the opening notes.
Yes, I put down "how do you find him?" which is correct English and conveys the same idea.
"How (do I, do you, does one, etc.) find him?" Any English translation of this Vietnamese sentence needs to supply an expressed subject to be complete and idiomatic.
làm sao = how
tìm = find
anh ấy = him
the best english translation in my opinion would be:
"How do you find him?"
Since how to find him doesn't really make sense and "you" doesn't have to refer to YOU but can be a collective you.