Barry
You can try the magic wand tool, make sure the "+" is selected.
Select all the interior white, then choose "selection , convert to object".
Now choose "edit, trace edges, image". You will now have a path object
of all the interior parts which you can apply 3D to.
By selecting all white interior and exterior of your line art and choosing
"selection, invert" before converting to object you will extract only the lines
and can use trace to convert them to path object and 3D.
Failing that you would have to use path tools to manually trace line art.