How to find configuration files?
Solution 1:
You will just have to find the name of package particular service comes from dpkg -S <Any file you know and think comes from that package which provided the service>
cat /var/lib/dpkg/info/<package>.conffiles
This will help.
Solution 2:
You open the manual page for the command or service you want it for. The conf file for iscsi is iscsi.conf
I tend to assume a conf file will have {service/application}.conf. Most applications I use have something like that (with MySQL as the exception ;) )