I made this beautiful painting about 800 mm in length, so that it would look proportionally on the wall. In order for it to be printed on my Ender3Neo, I had to cut it.

Here are parts of the same picture. Each part needs to be scaled along the X and Y axes to the required size. I did it 200%. I did not change the scale on the Z axis, leaving a thickness of 2 mm.
Filling I recommend 20-25% triangles. At least 3 layers from the bottom and top. Now it seems to me that it is possible not to print perimeters at all (but I have not tried it).

I added a LAYER containing all the parts at once, it is cut a little differently, try which option seems more convenient to you. I was printing a sunset.stl file