Chords are C, F, and G. If you prefer to play in another key they are 1, 4 and 5 (or tonic, subdominant and dominant) of whatever key you choose. Work the changes out by ear; it is an excellent exercise and not hard for this song. At a guess it would be:C,C,F,C
C,C,G,C
C,C,F,C
C,C,G,C
A