While importing data, is there any place in the documentation where I could learn how to match web user interface names such as "Supplier / Supplier / Id. Externo" with the actual column name that should be used in the CSV?

In the below example, I positively know that I want "Supplier / Supplier / Id. Externo", but I do not know where to look for the actual column name to be used in the CSV file.

An example image can be found here: http://snag.gy/465q8.jpg