what will be the total number of mitotic divisions in the formation of 64 daughter cells

A single mitotic division of a cell results in the formation of 2 daughter cells.
Thus, number of division in a single cell required to produce 64 daughter cells will:
         2ⁿ = 64
=      2ⁿ=2⁶
=     n = 6

Thus, 6 divisions are required to produce 64 cells.
It can be depicted as:

1$\Rightarrow$2 $\Rightarrow$4$\Rightarrow$8$\Rightarrow$16$\Rightarrow$32$\Rightarrow$64.