Extracting string from string?

I have a string that looks kinda like this:

string superCoolString = ""something.something.thisthing","something.something.thisthing","something.something.thisthing" etc..."

string superCoolString = ""something.something.thisthing","something.something.thisthing","something.something.thisthing" etc..."

And i need to get only the "thisthing" part how would i do that?