What does 在来自中 (zài láizì zhōng) mean in 在来自中、俄、美、英、韩等五国, ...?
中 is the short form of 中国 here.

中 = China

There’s a 顿号 (、) after 中 so you can tell that it is part of a list, that would aid your deciphering methods letting you know it’s not a phrase with the words in front of it.