How to insert .stp file / Replace 3d object tool

I am attempting to insert CAD models into a pdf using Acrobat Pro DC. The "add 3D object" tool allows me to use .u3d or .prc files. Unfortunately, my 3D models become enormous and faceted when converted to u3d. I am told that I can insert a simple .u3d cube object and then use a "replace 3d object" tool. I am told that the "replace" option will allow me to choose other filetypes such as .stp. This is my filetype of choice as it remains small, retains surface color, and does not result in faceted surfaces.

In the old days, I could convert .stp files to 3D pdfs using acrobat pro extended.

I can't find a way to do it in the new software.

Is anyone aware of a way to insert 3d filetypes other than .u3d or .prc?

Or, where this "replace 3d object" option is?

Also, I'm on a windows 10 machine...

Thanks in advance.