I want to Upgrade graphics card

There is no graphics card (board) like the older 2011 models. Your only option is replacing the logic board its self as the GPU chip is soldered to it.

• The low end i5 2.9 GHz model has a NVIDIA GeForce GTX 660M
• The i5 3.2 GHz & i7 3.4 GHz models have a NVIDIA GeForce GTX 675MX
• There was an option on the i7 3.4 GHz NVIDIA GeForce GTX 680MX model for an additional $150

Frankly, If the graphics is holding you back then I would look at finding one of the better 2012 models used or something newer. Often times its the RAM and/or storage that needs addressing to gain more performance

What is the amount of RAM you currently have as well as your storage (HDD, SSD or Fusion) as well as its size.