If you're referring to the 5-digit Signature PIN to electronically sign your return on a screen with "today's date" and your birthdate, you don't have to use the same one as last year (aka "Prior-Year PIN"). You can make up a new one.
If you do want to use the same one as last year, we can tell you how you "might" be able to find it. Did you use the 2023 Online TurboTax or the desktop version?
