This is a guess because I can't see the PPI of the original image. But it's kind of obvious what has happened.
The original image is 8.5" x 11" @300 PPI (2550px x 3300px), which is exactly the same as 35.42" x 45.83" @72 PPI (2550px x 3300px).
TLDR: The images are in fact the same size.
Only the PPI has changed. When PS exports a PNG, it exports it at 72PPI because it's the default for web images, although in fact the PPI setting is irrelevant for images on the web. Images in web browsers display at the native screen resolution of the device they are being viewed on.
If you don't understand why, I suggest you read this The Myth of DPI - it's an old website but still very relevant.