Export a section defined by a reference plane to a DXF

Hello,

I have a part which consist of a solid surface, and I have been trying to use the same advice as in https://forum.solidworks.com/thread/53142 but, I don't get the Insert Surface Cut enabled on my menu

Below you can see an image of what I get.

Is there another way to obtain a DXF of a required plane?

Thanks in advance

SolidworksImport export