You need to define variables where you will store any of your reading or values.
Like jimboZA suggested.
Before any "else if", there is always an "if", curly brackets follows your "ifs".
As for printing on the serial port, you need code lines like
Serial.print(" name of your variables");
Remember any single expression counts in the programming language.
// ---> used for commenting anything you'd like to : you will observe that with the IDE, changing the line color to light grey, meaning inactivated.
// Any comments goes here.