A question related to writing of SoP I am going to apply to some US universities. So SoP is one of the important things in the application procedure. My question is related to this topic. 

So, after completing the Ms degree (from University X), I will be a first year PhD student at some other University (say University Y). However, I am still looking for an US University for Ph.D. Now, as a student of University Y, I have read some topics which are considered advanced in my area of preference, that's to say these topics are bridges between the Ms degree and the Ph.D. degree. 


  Should I include, any sentences like this in SoP, "I have done some
  credit courses like a,b,.... at University Y as a first year Ph.D. student".


Thanks in advance.
Since the SoP is intended to detail your goals and path ahead, you could say something similar to that if those topics support those goals specifically. But if those courses are also in your CV or transcripts it will also be known that you have studied those things. 

However, detailing that you studied them as a doctoral student is less useful. But, after mentioning your intended sub field of study you can certainly say that you have taken certain advanced courses in that field. 

But in general, make the SoP focus on the future, not what you have done in the past. Other parts of the application will detail your past accomplishments.