Ubuntu Linux version 18.04 LTD will EOL this month's end unless you buy extended support. Here is how to upgrade Ubuntu 18.04 to 20.04 LTS https://www.cyberciti.biz/faq/upgrade-ubuntu-18-04-to-20-04-lts-using-command-line/ and 20.04 to 22.04 LTS https://www.cyberciti.biz/faq/upgrade-ubuntu-20-04-lts-to-22-04-lts/