IPv6 doesn't oficially have NAT. There is the EXPERIMENTAL RFC 6296, IPv6-to-IPv6 Network Prefix Translation, but it is not the NAPT that most people assume. It is a one-to-one NAT.
There are some real problems with trying to use NAT on IPv6, and some are listed in the RFC.
NAT is a kludge to extend the life of IPv4 until IPv6 can become ubiquitous. NAT breaks the IP end-to-end paradigm, but there are not nearly enough IPv4 addresses for that. IPv6 give you an almost unlimited number of addresses in order to restore the IP end-to-end paradigm, where every host has a unique IP address.
Some network devices, and some host OSes have NAT for IPv6, but read the RFC to understand the problems this can cause.