Your /etc/apt/sources.list file is configured for Ubuntu 20.04 (focal) but you are running Ubuntu 18.04 (bionic). Please modify your sources.list file for bionic and try the upgrade again.
Your /etc/apt/ sources. list file is configured for Ubuntu 20.04 (focal) but you are running Ubuntu 18.04 (bionic). Please modify your sources.list file for bionic and try the upgrade again.