Physics help please?

if i can remember there is an equation this is a really simple problem. f=1/T set that equal. .38=1/t so t=1/.38 where t is time. ok just found it the period is T=2pi x sqroot (L/g) so L=(T/2pi)^2 x g where pi=3.14159 T=1/.38 and g =9.8. havent checked the answer but hope that helps.