Can anyone please help with this?
Here’s a single start. Note this could be done a number of ways.
Here I created two spirals using the Archimedes Spiral tool in the Curve Maker extension. I connected the ends with edge segments, used Curviloft to create a surface and then Vector Push/Pull in Joint Push/Pull to extrude the shape downward.
Another option: A single Archmedes spiral with Curve Maker, a rectangle for the step profile, and Eneroth Upright Extruder.
That helps! Thanks a lot DaveR!