Update Joomla Website from Joomla! 2.5.11 to 3.0 or 4.0

I have an old joomla website running on Joomla! 2.5.11 . I'm looking to upgrade to the newer joomla version to get rid of issues anf glitches. The site will need to be recofigured too i'd think as the formatting might be lost which would be something to take into consideration. The site is http://tigersharp.net - thanks