You can't.... SolidWorks 2012 and 2013 can only open up to NX 7.5.
I am not near my SW2014 install to be able to see what version of NX it can open.
What you can do in the meantime is download Autodesk Fusion 360. It is free for slightly less the 90 more days. After that it is $25 per month per user. It can open NX 8.0 files, and I think NX 8.5 as well, then you can save out a step or iges file to bring into SolidWorks.
Or..... If you can post your file here. There are some folks that have access to NX 8.0 that may be kind enough to translate the file for you.
Depends on how quick you need the file.