How to upgrade your Joomla 2.x.x (Older Major Version) website to the latest stable 3.9.x release

Migration to new major version is slightly "dangerous movement", because you have to be sure that all your Joomla extensions support the latest version of Joomla. This means that after you finish the installation some parts of your website can be inoperative.

Important! Never start migrating without making a backup of your current Joomla website! Because you can lose everything.

• Log into Joomla! admin.
• Go to "Components" -> "Joomla Updates" or simply paste this link http://yoursite.com/administrator/index.php?option=com_joomlaupdate into your browser, this will take you directly to "Joomla updates".
• Because there is still no long-term release of Joomla 3.x branch, you will have to switch to short-term release settings for the update server. For that click on "Options" and from the drop-down list, click on "Update server", choose "Short term support" and click "Save and close".
• After saving Joomla will automatically start searching for available updates. Press the "Install" button to start the migration. Joomla will take a few seconds to migrate your content. After migration finished, you will see the new Joomla 3.x admin panel.
• Go to System ->Maintenance, Clear Cache and Purge it!
• Go to Extensions ->Extension Manager, then on the "Update" tab press "Purge cache".
• Repeat the migration process again.