.rpm works only on Red Hat Based systems, Ubuntu is based on Debian so it uses to .deb versions.
For you currently it is no longer possible to upgrade to a newer version of Ubuntu by directly invoking
apt-get upgrade
cause your version is too old.
In case you need to use MySQL also, I suggest you download the latest version from the Ubunu site
Cause otherwise u would need to manually compile and install all the software you need.