I know how important to save this PIN, @redhead1_8. I can help you where to obtain the 10-digit Efile number in QuickBooks Desktop.

As mentioned above by @bigred, it cannot be retained in the QuickBooks Desktop account when you upgrade your subscription. Thus, we need to reach out IRS to obtain this PIN again.

I'm also adding this page about paying your federal taxes in QuickBooks Desktop: E-file and e-pay federal forms and taxes in QuickBooks Desktop Payroll Enhanced.

Ping me in the comment section after trying these recommended steps above. I'd be delighted to assist you further.