How do i make this file ready for 3D printing?

How can i make my design ready for 3D printing? ive tried taking it into Rhino but it says that my angles done match up. Im not good enough to make my whole design again more simple for 3d printing. Any tips how to remake or fix it for 3d printing?
New to this forum! how do i upload my file to this??[outline version~~.skp (1.1 MB)

7th icon to the right.

Us looking at the file, and maybe doing the fixes, would solve the immediate problem. But out of curiosity, is there any way to get Solid Inspector features into the Free version?

Orient faces and check for surface borders, stray edges, and internal faces. Make sure it’s a solid component in the entity info.

It’s implemented in the school version already, maybe it will find its way to the free one too?

Hello @stellacarrclarke,

In order to 3D print the model, it must be a Solid
See this topic…

As it is, the model you shared is far from being a Solid model.

Generally, it’s quicker and easier to start over than it is to fix such things.
Albeit, it is possible, with no small amount of tweaking geometry, to make the model a Solid.
See this section of the SketchUp Sage site…