13.04 has a good number of extensions in the Ubuntu software center .
After running the command open the Tweak Tool and enable the ones you want.
sudo apt-get install-gnome-shell-extensions
I can't help with the themes unless you know the source because the Ubuntu repository only supplies the official default themes. Installation instructions often change from one release to another so knowing the name of some of the themes you had will help . I have about 40 themes installed from different sources.
Additional Extensions: https://extensions.gnome.org/