Hi,
HikaShop has a migration tool in the menu Products>Import, under the RedShop import tab.
It can import everything.
Now RedShop was not used a lot and so not many people migrated with it so there might be some issues with your version of RedShop.
The best is to first make a copy of your website and install the latest version of HikaShop on it. Then, try the import tool and see what you get.
If that goes well, you can do it on your live website, move to HikaShop, and then update your Joomla to the latest version since HikaShop's latest version is compatible with both Joomla 2.5 and Joomla 3.x.