you need to using jomsocial 4.1.2, only at jomsocial 4.1 we have that feature.
you can find it at jomsocial backend > theme designer > profile > Enable profile card
all files under /components/com_community and /administrator/components/com_community and all jomsocial modules and plugins.
my suggestion please make test site and copy your site to there and try to upgrade the jomsocial.
if any problems we still have time to fixing it.
as long you dont have any core hack at jomsocial files. it suppose to no problem to upgrade it.