If/Else statement (Mute Button Unity 3D)

I am trying to create a mute button in my game in Unity, but I'm running into a few problems. I need to create a if/else statement, to show when the button is press mute the audio and display this image, and vice versa.

I am guessing I should put my if/else statement into my onClicked method, but not for sure where to start from there.