read int/long from sd card

hey!!
i got this working. now i can read integers from SD card.
only problem is now to implement this same thing to use with
looong string of numbers. for example : 123123123123123123123123123123123
i would like to use this same method in function or in loop, but i dont know how ..
i would like to add REAL integers from sd card to array like
byte array1[8][16] = myFile.read();
i know i can do it somehow in double for loop (if im using two dimensional array)
but i have no idea how to divide long string to smaller pieces, and how to deal with these
variables.
char fileStr[] = "987654"; // example of what is in the file
char result[7]; // value are between 0/999940? so lenght is 6 characters + 1 ('\0')
uint8_t i = 0; // a counter