convert STD c++ code into C with String library

I have problem converting this code snippets into arduino compatible code

      string * octetArray = new string[(byteString.length() / 8) + 1];
        string * restArray = new string[(byteString.length() / 8) + 1];
        string * septetsArray = new string[(byteString.length() / 8) + 1];
        
        for (pos = 0; pos < byteString.length(); pos += 8) {
                octetArray[pos/8] = byteString.substring(pos, 8);
                restArray[pos/8] = octetArray[pos/8].substring(0, septetCnt % 8);
                septetsArray[pos/8] = octetArray[pos/8].substring(septetCnt % 8, 8);
                                
                septetCnt++;
                if (septetCnt == 8){
                        septetCnt = 1;
                }
        }

byteString is an arduino String object

thanks to anybody that can help me,