Go to https://www.prusa3d.com/, click on software and select your OS. Install the prusa slicer.
This software is a "slicer", it is used to prepare the 3d model to be 3d printed, to transform the STL file into a G-code readable for the 3d printer.
But in our case, we will just use this software to edit the 3d model. But of course, if you have a prusa 3d printer you will also use this software to 3d print the slices.
So open the .STL file that you have just saved with SLICER.
Click on file, then import STL/OBJ etc ...
Click on rotate and turn the model 90° to put it vertically.
Once it done click on cut and set the thickness you want, I set 10 mm.
Finally click on perform cut.
You will obtain that.
Now select the model and cut a slice again, organize the slices as you want but it is better to do it in the cut order.
Right click on each slices one by one and export as STL.
And that's it, now you have all the slices ready to be 3d printed where you want.
You can find a friend or a member of your familly which have a 3d printer or use an onlise service like shapeways or sculpteo for example.
An example of a 3d printed nasal cavity.