I'm writing my doctoral dissertation here in the United States, and quoting some text from an English-language paper written in Germany. In Germany, the convention for writing numbers is to use a comma as the decimal separator (3,5 meters), but in the United States, the convention is to use a period as the decimal separator (3.5 meters).
Is it appropriate to reformat the numbers to the American convention when I quote this paper, or is it more appropriate to leave it as-is?