Well, just do a clean install, after creating a new DB, and if everything works
as planned, then, you'll need to get all the Products - and User - Data from the
old Version DB, by use of a DB-Converter. This Converter will then adapt + paste
the old Version Data into their correct Place and Format in the new DB, to make
it usable in your new Version Shop. And then, you may remove the old Shop, and
the old DB, since it is no longer of any use.
Many Dev's offer upgrade services, but you better depend on peoples like Peku (pekka2),
and/or other wellknown OC-Pro's, after all, one has to make sure, not to let 'Unknowns' handle
sensitive User Data, working trough anonymous eMail Accounts, to hide their idendities, for
what fishy reason ever...
One more thing, just don't try to use any formerly used VqMods, Modules, or Themes, 99+% won't
work anymore, and you have to check, if newest Versions Extensions exist. And decide on using
OcMod only, if you plan to install Extensions again, it's of absolutely no use, to have VqMod and
OcMod (installed by default), working on the same system. It would only be a double - doing the
same procedure, and double-doings always only cost Performance, and possibly add to problems,
since, after any changes, both Caching-Systems have to be resetted, to make something work again.
But most don't have a Clue about this, and then come here, because changed Content will not be visible,
after only clearing out one of those Cache Sections. And that TWIG Theme Thing uses it's own Caching,
so, there is even more to clear out in OC-3, after some changes have been applied to the system ...
Just to mention this too ...
https://www.opencart.com/index.php?rout ... n_id=24347
https://github.com/pekka2/OpenCart-Migr ... grade-Tool
https://www.opencart.com/index.php?rout ... n_id=31384
https://www.opencart.com/index.php?rout ... grade%20DB