You need something to split the guitar signal to go to the inputs of the three pedals and the dry input of the mixer. Either a passive splitter, or a switcher like the Mini Effect Gizmo. The Mini Line Mixer will connect to the outputs of the three pedals and mix them with the dry signal.
Unfortunately, I don't know how his board is wired.
Either a passive splitter ?Unfortunately, I don't know how his board is wired.