Hi,
HikaShop is working on Joomla 2.5 and Joomla 3.x ; so there is nothing special to do.
You will be able to find a lot of threads talking about that specific migration and also links to tools or components to help to perform the Joomla migration.
But regarding HikaShop, the component is compatible, the database have the same structure etc. You just have to be sure to use the same version and not perform an update during the migration process.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.