I'm not entirely sure as I haven't read it myself. But generally, novels with a title like this might be about a search or journey related to paradise (jannat in some languages). It could be a spiritual journey, or perhaps a more metaphorical search for a utopian or idyllic place.
Another option could be to ask in book clubs or among friends who are into reading novels. They might have a copy or know where to get one. Some specialized bookshops that focus on regional or niche literature could also be a good place to search.
It's hard to pinpoint exactly where Gojo is at any given time in the manga. His whereabouts change as the story progresses and different scenarios unfold. It could be in a supernatural realm, a mission site, or interacting with other characters.