Salieron no se sabe de dónde unos hombres con sombreros de anchas y la típica indumentaria.
Why is salieron put in the front of the sentence, can we say "no se sabe que de dónde salieron unos hombres..."? Thanks a lot.
2 Answers
Excellent questions zhou, I would also like to thank you for always taking the time to use correct punctuation, spelling etc. 
And I can see you are learning veeeeeeeery fast, yes, the suggested sentence would be correct
The most common way:
Unos hombres......salieron no sé de .....
Not only is the original correct (as Heidita pointed out) but your alternative is not correct. "saber que" would need to be followed by whatever it is that people/someone knows. The same is true in English You can say "they came from who knows where ..." but not "they came from who knows that ...". In many cases in English, you can omit the "that" ("I know he's coming." vs. "I know that he's coming." However, the reverse is not true (you can't always add "that") e.g. "I know who you are." vs. "I know that who you are."
Spanish is less flexible in this respect. If you're specifying what it is that you know, you need the "que" but if the statement as simply about your knowing/not knowing (an unexpressed) something, you omit the "que".
