Hi, you can download cura and meshmixer for free.
There is a lithopane code in Instructables site that uses Processing (free as well) : you can turn a greyscale picture into a stl model.
Then try and cut it in meshmixer.
Then "slice" it in Cura.
I think this last step will create a lot of questions : there's a lot of parameters to get familiar with.
You can play around a bit with this process but let's be honest you'll have to actually try and print to learn by trial and error the stuff that won't work and the go arounds.
Expect a little frustration at first. But we can help.