If you have a reduction lens like the one /u/John1976mtl shows it should screw directly into the cam (yes, C-mount) and then pop directly into the trinoc tube on your stereoscope. You don't need the other accessories in your photos. This is the one that comes on cameras like yours.

Not sure if this works, but this is the one I’m using with my microscope camera

HAYEAR 0.5X Reduction Lens Eyepiece Lens 23.2mm Mounting with 30mm 30.5mm Ring Adapter Applicable for Biomicroscope Stereo Microscope https://www.amazon.com/dp/B06XZ2TQ98/ref=cm_sw_r_cp_api_glt_fabc_PFTQC9SF2JS44TGDMD8E