You're trying to use your mutable string like an array. Try the following:
NSMutableArray *array = [NSMutableArray new];
for (int i = 0; i < 100000; i++)
{
NSMutableString *myString = [NSMutableString new];
[myString appendString:AllmyData[1][i]];
[myString appendString:AllmyData[2][i]];
[myString appendString:AllmyData[3][i]];
[array addObject:myString];
NSLog(myString);
}
However, that'll result in 100,000 log statements. Are you sure you want to do this?