Do I understand you right, you need a list of packages installed on one system, so that you can install the same packages on another system?
In that case you can get the list with
dpkg --get-selections > installed_packages
If you want to setup another system the same way just copy the list to that system and do
dpkg --set-selections < installed_packages
All these actions have to be run as root, of course, so you may have to put sudo in front.