Welcome to the Bunnings Workshop community @Arizona1984. It's great to have you join us and many thanks for your question.
You'll most likely find that you need something more substantial than 3M self-adhesive to mount this shelf unit. I would suggest attaching one of these Zenith 20mm Zinc Plated Angle Brackets per cube to the wall with Macsim 8mm Yellow Zinc Hollow Wall Anchors. You'll need to position the brackets at the corresponding heights of the three shelves. Allow the bracket to hang down to form an L shape. Place the top panels of shelving unit onto the brackets and screw through the bracket into the underside of the shelf.
If done correctly the fixing and L bracket will be hidden by the thickness of the timber.
Please let me know if you need further assistance or had any questions.
Mitchell
