we have that
10 mm is equal to -------> 1 cm----> multiply by 100
10*100 mm is equal to -------> 1*100 cm
1000 mm is equal to -------> 100 cm
and
we know that
100 cm is equal to-------> 1 m
therefore
1000 mm is equal to -------> 100 cm
100 cm is equal to-------> 1 m
1000 mm is equal to--------> 1 m
X mm-----------------> 7.5 m
x-7.5*1000-----> x=7500 mm
the answer is
7500 mm