Hi,
What you can do is this:
- migrate the Joomla user accounts from one website to the other with the tool of your choosing. If you don't, the users won't be able to login to access their order history, and purchase again with their Joomla user account. They'll have to either purchase as a guest or create a new account. There are several extensions on the Joomla Extensions Directory to be able to do that.
- export the hikashop tables of your old database via your PHPMyAdmin.
- if the table prefix is not the same on both website (setting in the Joomla configuration), you need to edit the exported file with notepad and replace the prefix of the tables to use the new website one.
- import the file in your new database via your PHPMyAdmin.
- install the latest version of HikaShop and skip the installation wizard. When doing so, HikaShop will link the users with the Joomla user accounts if possible, fix the tables to use the new structure, etc.
- you also want to download/upload the files / folders in media/com_hikashop/upload/ and images/com_hikashop/upload/ from the old website to the new website in order to get the product and category images, as well as other files you might have uploaded through HikaShop on the old website.
Once all that is done, you can just configure HikaShop menu items and / or HikaShop modules via the menus / modules Joomla manager in order to access the categories / products / cart / checkout etc and you should be good to go. You'll probably have a few things to configure / update like the checkout workflow or the HikaShop cart notification plugin as these were not available in the old version of HikaShop you were using and thus might have a different default behavior than what you had configured in your old HikaShop.