Cannot select and export 3D voronoi cube as .stl

Hello, I am pretty new to Rhinoceros and Grasshopper and am trying to create a 3D voronoi cube to export in .stl format and 3D print.
I started by using an existing .gh file:
However, I cannot select the object to export and if I try to “save as” .stl format I get prompted “No surface objects to export”. I already checked that there are no objects locked. I tried other files and always get the same message.
Can you help?
Thanks in advance!

Grasshopper objects don’t exist in the Rhino Document until Baked, Right click the last component and bake to a layer. Then you will be good to export.

do note that 3D printers typically want a single closed object, you will end up with a bunch of cylinders at this point.

That solved it, thank you so much!