I would do it like this :
#include<stdio.h>
int main()
{
int years, months, days, hours;
scanf( "%d", &years );
months = 12 * years;
days = 365 * years;
hours = 24 * days;
printf( "%d years is %d months\n", years, months );
printf( "%d years is %d days\n", years, days );
printf( "%d years is %d hours\n", years, hours );
return 0;
}
The key thing being these are all integer values. They do not need to be floating point.
It is important to note this code does not take into account leap years.