I have an NSString that is of the following pattern:
Hello
No.: 123456789123
Age: 21
Country: xxx
How can I search within said string so
I think [yourString substringWithRange:[yourString rangeOfString:@"123456789123"]] should give you what you want.
Presumably you have a variable with the value "123456789123", in which case you would do [yourString substringWithRange:[yourString rangeOfString:otherString]].
For more information, see the NSString class reference.