There are numerous ways to talk about community in Ted Conover's book Newjack.
One way to think about community in prison is by taking a look at who is excluded from the general community.
One type of people who were exiled from the greater community (and thus put in great danger) were "snitches" or "rats." When Conover tells about The Box, or solitary confinement, he mentions how half of the men there were "under protective custody." These inmates asked to be protected. They were rape victims or victims of other assaults who had "identified their assailants."
Expelled from the community, these "rats" could no longer enjoy the protection of the community. Yet perhaps we need to modify our understanding of community. Perhaps community in jail doesn't keep you completely safe in the first place. After all, if these victims were a part of the community at some point, why were they raped or assaulted?
Again, perhaps community doesn't guarantee your safety, but it could put a threshold on what can happen to you. You can be raped, but not killed; assaulted, but not murdered.
You might want to think about other communities where people are a part of the same group and also subject each other to a degree of harm. Maybe look at hazing in fraternities or on football teams.
When thinking about communities in Sing Sing, you might also want to take note when Conover brings up gangs. How do gangs function as communities? What is the difference between a gang and a community? Couldn't the Latin Kings or the Bloods be called a community just as well as a gang? How might race or location (like a jail) influence whether we deem something a gang or a community?
On a less violent note, you could notice how communities prop up around sports or card games. Conover notes the “big basketball scene". In this context, communities in jail seem to resemble those outside of jail: both are built around a shared interest in a sport or hobby or TV show. Remember, some of the inmates love the soap opera Days of Our Lives. They watch new episodes together, like a community.