In this case, first we need to know the equivalence
[tex]1m^2=1000000\operatorname{mm}^2[/tex]Then for our case
[tex]\frac{25.4\text{ m}^2(1000000mm^2)}{1m^2}=25400000\operatorname{mm}^2=2.54\times10^7\operatorname{mm}^2\text{ }[/tex]ANSWER
25.4m^2=25400000mm^2=2.54x10^7mm^2