In Night, on what page is "the stars were but sparks of the immense conflagration that was consuming us?"
Whenever dealing with page numbers, I think that it's impossible to get a definite answer. Different editions of the text are printed and pagination with such varied publication.
The quote in which Wiesel describes life in the ghetto appears early on in the text. It happens when Eliezer and his family have left Sighet. Inside the small ghetto, the chaos of resettlement and the insecurity about what will happen next grips the community. The quote comes after Eliezer's father had refused the help of the family's former maid. She offered a plan to escort the family to safety in a remote village. Eliezer's family refused. Since the family did not want to be split up, they remained together. From this point, the description of night in the ghetto emerges. This is the point where the quote in question appears:
NIGHT. No one was praying for the night to pass quickly. The stars were but sparks of the immense conflagration that was consuming us. Were this conflagration to be extinguished one day,nothing would be left in the sky but extinct stars and unseeing eyes.
This quote helps to bring out the recurring motif of "night." Its function in the text is to operate as one in which darkness and uncertainty shroud those who must endure the horror of the Holocaust. It is this brutal insecurity that defines the Holocaust in a psychological manner. The "unseeing eyes" is an image that alludes to the sheer terror of the Holocaust.
The page number is going to be different and dependent on the version you have. In my version, I have it on page 21. Yet, I would pay attention to where it appears in the narrative sequence. Look to the point where the family has been moved to the ghetto. It helps in that the opening of the paragraph where the quote appears has "NIGHT" in capital letters.