How to upgrade license for image from standard to enhanced license? And how can I get license code?

Hello,

I would like to ask how can I purchase images from Standard to Enhanced license for just individual image that I need? Also, for standard license, is there a way for me to access to the license code for the Standard license?

I go into the License History page but I could not see where I can get the license code for Standard license, and also to upgrade it. 

Thanks for helping!