I need to make a mold

yes, i scale things back down to the normal size once i am done with all my cutting, editing, etc. None of my slicers give me the option to import it to mm or cm. they just say “you file is to large. Please scale it down” so i just do that in SU before i export the stl.

As for the mold, here is a pic of what im trying to do. The bottom left piece, the one he is not working on, is a mold of the inside of the mask, then once he removes the blue 3d printed mask from the second piece, it will be a mold of the outside of the mask, he then puts the two molds together, fills with silicone and then puts weight on it.

or maybe there is an easier way to 3d print a mold? maybe i need to go back to step one again?

I guess you need to figure out the shape of the surface you need for the part line. In this case it looks like it would match the curve of the mask.