I don't think so, because वे is explicitly 'they'. How many are there would just be कितने हैं?
This feels like an overly literal translation to me. It is much more natural in English to ask "how many of them are there?", to me at least.
Perhaps nowadays, but this is a perfectly acceptable sentence, though somewhat old-fashioned, it's true.
Old-fashioned sentences should not be default answers though it's fine for them to be accepted answers.