How do i recover the emails that were in my mailbox before you changed everything?

I had emails for bills that needed paying, now they are gone as I cannot change back to classic and I don't like this NEW yahoo. All my folders are missing, they had receipts in them for bills I had paid and now I don't have access to them. I had to change my email address, so now all my bills will not come to my old email address, and I won't get them. As I opted for online payments and auto pay, these will not be able to reach me now!!! I HATE THIS NEW YAHOO, PUT ME BACK TO CLASSIC!!!