Primary and secondary DNS numbers are state and, often, ISP specific. You can use Open DNS, but I would call your ISP to obtain the correct info for your device. Just ask a tech there, they will tell you.
If not, Google "dns server lists" and you can find public ones.
Open DNS, in case you want to try it:
Primary: 208.67.222.222
Secondary: 208.67.220.220