The others who have responded to your plant ID question here, are
correct - It's a poppy. When I was a kid, my mother grew loads of that
type of poppies. I never knew the "official" poppy name like the other
posters gave you. They are much larger and the plants are larger, than
most poppies that we see. The blooms are usually about 4 - 5" across.
I remember not seeing any of those poppies for several decades, and
then about 3 years ago, I bought some wildflower seeds and put them out
in in a section of my yard, and one of those poppies came up. I was so
delighted to see it. I tried to successfully collect the seeds, and
replant - but I failed.
I'm glad to see the other posters post the "official" name of them. .
.Perhaps I can locate some seeds on the internet.