Gst applicability on bill

Dear Sir,

I want to know that If I am a Registered Dealar in West Bengal and I going to Bihar for purchased a Goods but in that time I have received a order for same goods  from Uttar Pradesh and sold to same goods to Utter pradesh  by Transport without goods brought to west bengal. How I charge GST on That Bill. I am confused on above problam. Kindly anyone help me please  and what rule are applicable on it.