Hi,
Normally, you do that like this:
You put in place your new Joomla 3 website, and you export/import the users (you'll find a few extensions for that on the Joomla Extensions Directory) from the old website to the new website.
Once that's done, you export the hikashop_ tables from your old website database and import them on your new website database via phpmyadmin.
Then, you copy the folders images/com_hikashop/ and/or media/com_hikashop from the old website to the new website via FTP.
Finally, you install HikaShop on your Joomla 3 website and you should have all the data there and all that's left is to configure the menus/modules and the checkout.
I don't think that this needs any script.