NX CAD # tutorial 5.1
How to create core cavity, check this link
   • NX Mold Wizard #Extension Board Mold ...  
NX 10.0 for Engineers and Designers (MISL-DT)
https://amzn.to/2mf6GiI
Mold Design Using NX 11.0 : A Tutorial Approach Paperback – 1 Jan 2018
by Sham Tickoo (Author)
https://amzn.to/2kN0f68