Cutting an Stl mesh for 3d printing I'm a little new to blender so I need help.

I need to cut this mesh/solid stl file for 3d printing, but I don't know how to do it in blender. How would I go about cutting up a mesh into separate solid meshes? I've tried using the bisect tool and I was able to figure out how to cut a slice I wanted in the mesh, but I can't figure out how to make them two separate solid objects. Can someone help me?

Thanks
Either


Select the part you want to separate and press P Separate > Selection
Or press P Separate > By Loose Parts parts to break whole the object into all independent parts


You can quickly select all linked geometry inside the same object by selecting Faces/Edges/Vertex and then pressing Ctrl + L, or by hovering the cursor over some peace of geometry and pressing L