Hi Arif,
The answer lies in your LCD datasheets. For most of the HD44780 compatible LCD's the line 1 starts at 80H and line 2 starts at C0H. Your datsheet says
However for the 1:16 mux, the display has to be treated as a two line unit.
Thus the first 8 characters belongs to first line thus address are 80H to 87H The next 8 characters belong to second line address are C0H to C7H.

Regards,
Prahlad Purohit