Sorry this is a basic question. I do not know where does \label write the data to?

In my previous installation of MikTex 2.9 I can use \CJKnumber{\ref{X}} to reference a previously defined number X and CJKnumber will change this number into Chinese character. But the present installation cannot. It said the number \ref{X} is undefined. Therefore I want to check whether does \ref{X} really exists.