Almost. The path needs to have the correct syntax used by Acrobat JS for
files, and must also end with ".pdf", so something like this:
cPath: "/c/extr/page" + 1 + ".pdf"
(I'm assuming here you're running this code from a batch process. If not,
you'll need to place the entire thing in a trusted function, as is explained
in the Reference)
Also, when you extract a page it is not automatically opened, so there's no
need to close it.