No upgrade option in Update Manager in Ubuntu 9.04

While working on a project recently, I had a need to upgrade to the latest version of Ubuntu. I followed the following steps mentioned at the Ubuntu help page.

• Start System/Administration/Update Manager.
• Click the Check button to check for new updates.
• If there are any updates to install, use the Install Updates button to install them, and press Check again after that is complete.
• A message will appear informing you of the availability of the new release.
• Click Upgrade.
• Follow the on-screen instructions.