此句为定语从句,主句为：The address was in China,而且是过去式.从句为：to which….
因为定语从句which后要接一个完整的句子,所以可以先翻译句子意思为：……….以前到（去）的地址在中国.
由于没有上下文,所以有很多可填答案,以下仅供参考：
The address to which the company had shipped products was in China.
The address to which he sent money was in China.
另外要注意,主句因为是过去式,所以从句可能是过去式或过去完成式,根据前后句子意思确定.
希望可以帮到你.