Parsing through data

I am interfacing my ESP8266 with Arduino Uno.
I am sending a GET request using ESP8266 and receive a lot of data through the serial connection(about 1000 characters) .
I want a way to parse through all of this data in order to find the desired string(which lies between 2 other already known strings).
Is there any library for this purpose?
Or is there some program logic?
Also if the code is given it will brappreciated.

Possibly the below might be of use.