To fetch emails with the new (or old one) Gmail account do the same procedure:
Log into your new Gmail account.
Hit the gear icon.
Go to the 'Accounts and import' tab.
Go to the 'Check mail from other accounts' section.
Select 'Add a mail account'.
Enter your old Gmail account and hit 'Next'.
Your formula is correct except you should be using straight double quotes (" ") instead of curly double (“ ”) quotes.
This means your formula should be:
=IF(D2 = "Mrs.Winehouse", "firstname.lastname@example.org",
IF(D2 = "Billie Eilish", "email@example.com",
IF(D2 = "Jay Cutler", "firstname.lastname@example.org","")))
Straight " " VS curly “ ”
As the error message says, there is no way to transfer files between accounts from different domains but you could make copies using your G Suite account.
The basic steps are:
Using the personal account, share the files from the personal account to the G Suite Account
Using the G Suite account, copy the files
Transferring files across from ...