Welcome to the forum! But please edit your post and include code tags. See How to use the forum.
And as for the problem, Just check letter for letter. If a letter is right, check the next letter to the next letter. And so on. And if you make it to the end, you know you received the string you wanted to act on 
Ow, and be aware, a String is not the same as a string. To keep things easy, use a array of char's, that's a C-string
char checkString[] = "turnoffled";