I want to convert 3 digit integer like, 354 to string so to dig out each character (number) to convert back to integer.
You could use itoa() to convert the value to a string, and then subtract '0' from each character in the array to get the number, in each place, but division and modulo will be faster.
int n = 354;
int h = n / 100; // h = 3
int t = (n / 10) % 10; // 354 / 10 = 35. 35%10 = 5
int o = n % 100; // 354 % 100 = 4