Excuse me, are Uighurs a member of the Arab nation or a member of the Russian nation?

Neither. It is generally believed that Uighurs are a mixture of Uighurs, aborigines and Semu people who moved westward. Semu people include Arabs, and Uighurs also accept Arab culture, but only for normal ethnic blending, trade and cultural exchanges. Not for Russia. Except for a few Russians who are classified as Uighurs, most Russian immigrants are classified as Russians in China.