If you forgot the password to the Google Account that you used in your Google for Nonprofits request, you can reset the password
If you forgot which Google Account is linked to Google for Nonprofits, you can try searching your inbox for the Google for Nonprofits confirmation email. Search for an email sent from: firstname.lastname@example.org
If you're still not sure which account you used, request administrative access to your organization's existing Google for Nonprofits account. Your request will be processed in about 14 business days.