How can I get a replacement of LEGO NXT Green City Challenge Activity Pack CD-Rom?
If you are missing a component of a set supplied by LEGO Education, you have the following options:


Contact LEGO Education support (different support line than the
regular LEGO service support line) at
https://education.lego.com/en-us/support. Their US telephone number
is 800-362-4308. Plead your case there - they might have a digital
copy or remnant copies on hand. You would likely need to provide
details to make sure you have bought the original package (e.g. your
NXT license number).
Look on second-hand marketplaces such as BrickLink, BrickOwl or EBay to see if someone is selling the CDROM. I have looked for you and can only find 1 complete Green Challenge kit at the moment of writing this answer, so this route is not feasible.
Asking for someone to make a copy of a copyrighted work is (at least in most countries) illegal, even if you once purchased the original. 




NOTE: This is a Question &amp; Answer forum, and proper questions are those that offer generic guidance, not requests for particular favors. I have edited your question to better fit this format.