Sorry, no more upgrades for this system There will not be any further Ubuntu releases for this system's 'i386' architecture. Updates for Ubuntu 18.04 will continue until April 2023.
This guide is for you if you've seen the above message and you want to upgrade your Ubuntu system to 20.04 LTS.
This brief HOWTO shows how to take a working 32 bit 18.04 installation and convert it into a 64 bit system. You will be able to keep all your programs, settings and data. Once converted to 64 bit you can plan the upgrade to 20.04 LTS.