how do u find the no. of boxes that fit in the carton the volume of the carton is 1600000 and volume of box is 10000

That is assuming that the boxes fit exactly into the carton with no packing or spaces in between.

Divide the larger volume by the smaller volume.

$${\frac{{\mathtt{1\,600\,000}}}{{\mathtt{10\,000}}}} = {\mathtt{160}}$$