I can't sign in on my new ipad

Have you forgotten your credentials?

See: If you forgot your Apple ID  https://support.apple.com/en-us/HT201354 and

 If you forgot your Apple ID password https://support.apple.com/en-us/HT201487

You also can use Having trouble signing in/iForgot https://iforgot.apple.com/password/verify/appleid 

And you undoubtedly will need to see If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

Before trying to answer your security questions is very important that you think about your questions and their answers carefully and try to recall all details you can. If you don't answer them correctly enough, then you easily can lose control of your account.

What happens when you try? Error message(s)? More information would help.