Do I need to know my Apple ID for itunes

Check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID

https://support.apple.com/en-us/HT201354                  

OR see -> Having trouble signing in?

https://iforgot.apple.com/password/verify/appleid

See also this Apple article: If your Apple ID is locked or disabled

https://support.apple.com/en-ca/HT204106

Well it is never a good idea to forget your Apple ID. If you were signed into it, yes you’ll need it when you go to setup your phone again. Otherwise, you’ll have to prove it to Apple with proof of purchase that it’s your phone.

Write down your Apple ID if it’s too troublesome to remember it…

Yes. If you want to be able to use the phone, you will need to know the credentials for the Apple ID you were using on it.