The unit comes with everything for a standard installation worldwide.
You don't have a standard craft and need a custom installation.
If you have not opened the transom transducer mount package, I would recommend you exchange the Compact SI transducer for the HDSI transducer to get sharper images and better 800 kHz Imaging IF you want to use that frequency.
Next your hull needs a shoot-thru 83/200 kHz 2D transducer XP 9 20 for high speed depth/2D sonar.
You can attach the SI transducer above the hull bottom so it is protected from possible impact damage. Since Imaging is an idle speed or slower function, that transducer does not have to be at the bottom of the hull. If you have a jackplate, you can attach it there. It needs to "see" horizontally left and right.
You connect the two transducers to the display with the AS SIDB Y cable. That cable disconnects the 83/200 kHz crystal in the SI transducer and connects the shoot-thru in its place.
You can view lots of installations on the Bass Boat Central Humminbird forums in the Installation and Networking topic at the top of that forum. If you get lost, you can send me a picture of your transom with outboard tilted all the way up and I will edit the picture to indicate the proper location on the transom for the SI transducer.
I think your transom is still the triple step that earlier hulls have.