"pack" as in cub scouts...
There is no particular sign for "pack" as in, "a cub scout pack."
Some people might choose to sign a variation of the "family/team/group" concept by initializing the sign with "p" handshapes on both hands. I find that to be very awkward and unnecessary.
Instead I prefer to use the a sign I refer to as "CLUSTER." The "CLUSTER" sign indicates a general group of things. It can also be used to indicate plurality. For example, if I signed "MAN CLUSTER." It would mean, "men." If I signed TEACHER CLUSTER" it would mean, "teachers" in general.