Modify random password generator code

please i need your help to know how i should modify this code for being able to ask the user: the maximum number of numbers only he needs in the 12 characters_with_numbers password 2- the number of consecutive numbers in the 12 charachters_with_numbers password(for example if he enter 3, the password should not contain more than 3 numbers successively, but it can contains more than 3 they'll be placed in the password after a character between (at least).

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
int main() {
    char password[12];
    int i, j=0, len=sizeof(password)-1;
                        srand(time(NULL));
    printf("Your Random Password is: ");
    for (i = 0; i < 6; ++i)
        password[j++] = 'a' + rand() % ('z' - 'a' + 1);
    for (i = 0; i < 6; ++i)
        password[j++] = 'A' + rand() % ('Z' - 'A' + 1);
    for (i = 0; i < 3; ++i)
        password[j++] = '0' + rand() % ('9' - '0' + 1);
    password[j] = '\0';
    for(i = 0; i < sizeof(password)-1; ++i)
        {
        char c = password[i];
        j = rand() % len;
        password[i] = password[j];
        password[j] = c;
        }
    printf("%s\n\n", password);
    system("pause");
    return 0;
}