I dont want to mess any thing ,hence asking the question for clarification .
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To check if upgrading to the latest development release is possible:
If available run following command:
update-manager, then the Software Updater should provide you a notification for newly available Ubuntu 16.04. Click on Upgrade and proceed with the installation.
Since you do not want to mess anything you should consider doing a fresh install because 16.04 has many significant changes compared to 14.04, e.g. it supports ZFS filesystem. Also there are many deep rooted packages in 14.04 which might create difficulty during the upgrade.
You may like to have a walk through following links: