Trying to load world of warcraft, a message popped up that said i need a 3D accelerator card.

What iMac sub-model, and what video hardware is now installed. from "About this Mac..."

iMac made since Late 2012 have the graphics hardware integral with and soldered to the logic board--no "card." It cannot be upgraded without changing the entire logic board. The Wow SysReqs show you must have Metal-capable graphics hardware. Every iMac made since 2012 has that capability.

from the Blizzard site:

I think you are at the end of that computer's WoW days unless you run an older version.

Even though you have a socketed graphics card, I know of no Mac Metal-capable cards that fit that model. Apple added Metal at the same time they did away with "cards" and used integral gfx hardware instead.

I would ask in the WoW forums if anyone has found a workabout. Some Win laptops use the same form factor card as the one in the 2011 iMac but they would have to be "ROM-flashed" to work in a Mac, and I not sure if that still works with modern cards like it did in the old PowerPC days.

Incidentally, the 2GB card now in your iMac, if working, is probably worth more then the entire computer. I've seen them on the used/pulled market for up to US$500.

No, you could try but on a 2011 these are considered vintage by Apple and parts are becoming very scare. I'd give up on your current iMac and consider another computer.