It will come as tar.gz file to be manually unzipped with a program like xarchiver the (NPAPI version) there will be a file inside this archive libflashplayer.so - copy to /usr/lib/mozilla/plugins
Apt Installable Method
as I type this I notice there is a Ubuntu apt version which is installable.
Ubuntu 12.04 reached end-of-life in April. It will be best to upgrade to another LTS version first, like 14.04 (good until April 2019) or 16.04 (good until April 2021). It's kind of fighting a losing battle to try to maintain or upgrade packages in an out of date operating system.