No Mutants Allowed

Try things that have AI that do it, they usually fill in the "blanks." Google around for that.
Could start here. https://imageupscaler.com/

Ah thanks, I will give that a try. I want to size up some old game cartridge covers and book covers to poster size.

It's impossible.
Only alternative is AI like Squadcar said, and those basically "reinterpret" the image to upscale it and generate the details.