Can anyone tell me where aquaman starts post crisis on infinite earths? Like how Batman starts in Batman 404. Thank you.

That would be History of the DC Universe 2, but it's not an actual comic, more of a pictures book.

https://comicvine.gamespot.com/history-of-the-dc-universe-2-book-two/4000-27540/

The first actual comic would be the first issue of the 1986 Aquaman 4 issue mini series, the story where the "blue camouflage" suit was introduced.

https://comicvine.gamespot.com/aquaman-1-in-the-shadowy-depths-of-atlantis/4000-26446/