Question about a radiator plug

If there is one it will be on the bottom tank. If there is no drain plug remove the lower hose.

Because my mechanic keeps saying its behind the radiator in the corner on the drivers side because the plug we have dont fit should i replace the whole radiator

I would remove the lower hose and not worry about the drain plug.

So, your radiator is empty and does not have a plug in it? And the one you do have does not fit? Go to your parts store and buy a new one. You can probably replace it yourself but if you can't or don't want to, take the part and the radiator to a radiator repair shop and let them do it. It will probably cost about $25.