How do I detect a quoted substring in a string?

[SteveMann]

am trying to determine if a string contains a quoted substring.
This is my code that gives me a compile error: "ai3.cpp:162:37: warning: character constant too long for its type"

		//if the line contains 'class="wikitable"'
		string findString = 'class="wikitable"';
			
		size_t pos = str.find(findString);
                if (pos != string::npos) {
                        cout << "Substring found at position " << pos << endl;
                }

I've tried:

"'class=\"wikitable\"'"

but str.find doesn't find my substring.

So, can anyone suggest how I may search for the presence of a quoted substring?