Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
You don't need to create a new account. You can register/sign in using your original Amazon account, the one you used with your old Kindle.
If you have forgotten the password ***** your Amazon account (your email address), then you can reset the password ***** here --> https://www.amazon.com/gp/css/account/forgot-password/email.html
After resetting the password, register your Kindle with it. Let me know how it goes.