How many apples?

Number of apples in each figure is the square of the figure's number

Therefore, Figure 8 = 8 * 8 = 64 apples

$Figure~1=1^2=1$

$Figure~2=2^2=4$

$Figure~3=3^2=9$

$Figure~4=4^2=16$

$Figure~5=5^2=25$

$Figure~6=6^2=36$

$Figure~7=7^2=49$

$Figure~8=8^2=64$