Hi,
Well, it depends what you want to do, what is the time frame, etc.
Since you're on Joomla 3, the simplest and fastest is, I think :
- purchase a new hosting plan with the latest version of PHP
- purchase a Joomla template with Joomla 6 compatibility, if your current template is not compatible with Joomla 6.
- install Joomla 6 and the template on the new hosting plan. Ideally, you want to use the same table prefix as configured on the old website.
- you might want to migrate the Joomla user accounts with a tool:
extensions.joomla.org/category/users-import-a-export/
- configure the menus, Joomla articles, modules, etc to reproduce the structure of the old website
- if you use other extensions (like plugins from our marketplace place, or payment plugins from third party developers, other extensions not related to HikaShop, etc), install them too and then enable and configure them the same way as on the old website.
- migrate the "hikashop" tables from the old database to the new one with PHPMyAdmin. At that point, you might want to put the shop offline on your old website (with the setting in the HikaShop configuration) so that customers can't place new orders while you finish the migration.
- install HikaShop on the new website. It should automatically find all your data and settings.
- then, configure the menu items and modules for HikaShop on the new website similarly to what you have on your old website.
- you should now have something quite similar between the old and new website, and you can update the DNS record to point the domain name to the new website instead of the old one.
Doing it like this, you'll be ok for a long time. I would also recommend updating your Joomla version a few months after the release of a new version. That way, you don't have to manage the issues that can popup in the days following new releases, if any, and you can continue to update your hosting plan PHP version to keep the compatibility with Joomla, without having to do a full migration in 10 years because it becomes difficult to update an old Joomla to a recent one (that's your main issue at the moment I suppose: you can't directly update your Joomla to J6 because your current version of PHP is not compatible with it, and you can't update your version of PHP because your Joomla is too old and doesn't support it).