You can either check your local network (windows commandline: ipconfig or linux terminal: ifconfig) or visit a site to see whether you are inside a ipv6 network (e.g. http://ipv6-test.com/).

Note that ipv6 addresses are running out (europe's last /8 block has been distributed to >99,8%). Therefore some provider are using ipv6, providing you an ipv4 address via carrier-grade NAT.
This can lead to issues since you can establish an outgoing ipv4 and/or ipv6 connection, but might have issues establishing an ipv4 connection towards your home network.