Where is my Apple Newsstand purchase?

I decided to take a look at a magazine I had purchased some time ago through Apple‘s Newsstand app. 

The first puzzle is that I could not find the Newsstand app on my iPad. Looking online, I found the following:

“Newsstand was a built-in application on Apple Inc. 's iOS devices: the iPad, iPhone and iPod touch. It was dedicated to downloading and displaying digital versions of newspapers and magazines. It was replaced by Apple News in iOS 9.”

OK, that’s like walking into your home and finding out someone had rearranged the furniture, but whatever. So I look in Apple News and I don’t find any section for magazines I had purchased through the old Newsstand app. 

I look on my iPhone, which I no longer update, and the Newsstand app is still on there. When I launch it, I see a Library button at the bottom. I tap it, and on the next screen it says

“Your library is currently empty

If you are an existing subscriber, login”

I tap login and on the next screen it says

“To login or register for a Pocketmags account enter your email/username below:”

OK, I don’t recognize the name “Pocketmags.“ But I try typing in two email addresses I commonly use for registering, and in both cases it doesn’t seem to recognize the email and it tries to get me to create a new account instead.

How do I access my purchase from the old Newsstand app??