Which Torklift Scissor GlowStep Fits Carriage Cameo 36SB3

I am not finding what measurement to take to determine the correct model Torklift Glow Step to order. I have a Carriage Cameo 36SB3. It has a cut out well where the original step folds into. Do I measure to the top of the cutout well for the correct height, or to the bottom of the door. The existing 3 step is 10inch off the ground when the camper is level, and the last step up into the camper is 9, to big of steps for us older people. But I am not sure a 4 step will work? My measurement from the ground to top of the cut out well is 33inch Any information would be helpful. Thank you

asked by: Steve F