What will be my OBC-B;rank in wbjee of my genarel rank 61747 ?

You must have informed about your obc rank as well as your general rank in your result if you have correctly mentioned about your category in the form however you can predict your rank with the help of rank predictor but note that this might be different than your original rank so I would suggest you to again check your result. According to my assumption you'll get a rank around 20-30k .
https://engineering.careers360.com/articles/wbjee-result
Good luck!!