Where to upload?

Noob question: I've just installed Mijoshop, which uses OpenCart, on a Joomla website. I've bought a couple additional extensions for OpenCart and the first instruction is: "1) Unzip and upload the contents ... to the root directory of your OpenCart installation."
Where is this root directory?
I tried store/components/com_mijoshop/opencart but that doesn't seem to work.

Thanks in advance for any clues.

T

Probably won't work. The store root is the lowest directory holding its files (where the lower index.php and lower config.php are). That directory is probably second to even fourth above the root. Code and database will likely have been substantially altered, extensions FOR the genuine standalone OC are not written to encounter those changes, and probably will not work. What you have is what was OC, surgically amended, then imprisoned.

So are you saying that this extension I just bought - "Quantity Base Discount'" - will not work in OpenCart/Mijoshop?

Probably won't work. Since you already have it, look inside the .xml at what it expects to find and at what it expects to do instead. Then look inside the corresponding target files for what is there that will or won't match what it expects to find. If there is a dead match, then what it expects to do instead will work or fail or sort of flop.

for mijoshop, upload the files into com_mijoshop/opencart. They work like a normal OpenCart, but may need extra changes for the mod. Contact the developer and he / she will help you.

Normally, yes, ask extensions' and themes' authors. Be sure to mention to each author that this is mijoshop -- with joomla. Where you were already 3rd and 4th deep within store/components/com_mijoshop/opencart/ of joomla organization, when com_mijoshop/opencart/ failed in the first place, the odds are that files' code as well as db tables will differ significantly from what the extension authors dealt with in the first place, and will moreover destroy version correspondences.