Hi,
That is a very old version but it still should be possible to upgrade as long as you are not running a forked version of mojoPortal that has been modified. Our upgrade system is fairly smooth but if you do get errors most likely we can help you through them.
Backup everything first and read our upgrade guide.
Download the latest mojoportal .NET 4 MS SQL package and download our MySql data layer package. Prepare the files on your local machine first by copying the dll files from the mysql package into the wwwroot/bin folder of the main package and copy the /Setup folder from the mysql package into the main wwwroot folder to get the scripts for mysql. Copy the machinekey if it exists in your current web.config file and replace the one in the new web.config file.
Then upload the contents of the wwwroot folder from the package into the root of your web site as discussed in the article, once they are all uploaded visit /Setup/Default.aspx to run the upgrade scripts
Your skin will likely need some fixes from important skin changes article or to try new skins you would copy them from /Data/skins into /Data/Sites/[SiteID]/skins
Hope that helps,
Joe