In one sense, I believe that there is only one race. Scientists know that there is no biological basis for separating people into different races. Therefore, I do not really believe in the idea of race.
In another sense, I would say that there are three races, or at least there are three races that are easy to tell apart physically. There are white people, black people, and East Asians. These groups are easy to distinguish from one another.
However, what do we then do with all the other people of the world? What do we say about people like me who are part one race and part another? This is another reason why it is difficult to talk about races.
I would argue that while there maybe three or more races it is most productive to say that there is only one race.