You probably need two M5x10 or M5x20 with nuts.
You need to align the model to the Print surface and you need supports and 30% Infill. I recommend to print this in PETG. After printing you screw the part into the right side of the X-axis. It is very complicated to fasten the screws and nuts because of the x-axis rollers.
The author remixed this model.
I modeld a new X-axis attachment for the Elegoo Neptune 3. I then added links from Sneaks' articulating camera mount.