Konoha would most likely send out a search and rescue team immediately. This team would likely consist of some of their strongest ninja. For example, Kakashi might be sent as he has experience dealing with dangerous situations and is very skilled. They would also try to gather intelligence on where Naruto was taken in Iwa.
Another motive could be revenge. Maybe some in Iwa still hold grudges against Konoha for past conflicts. Since Naruto is a prominent figure in Konoha, kidnapping him would be a way to strike back at the village. They might think that by harming Naruto, they can make Konoha suffer.
One possible reason could be a threat from Iwa to Konoha. If Iwa was planning an unprovoked attack on Konoha, Naruto might take it upon himself to destroy Iwa to protect his village.
Naruto is obviously a very popular character in these fanfictions as he is the main character of the original series. In Iwa, characters like Deidara (who was originally from Iwa) often make appearances. His explosive jutsu and unique personality add a lot to the stories.
One great Naruto Iwa Admiral fanfiction is 'The Stone Admiral's Ascent'. It has an interesting plot where the Iwa Admiral character shows unique jutsu and strategic thinking. It really delves into the character's backstory and how they interact with the Naruto universe's existing elements.
Naruto could meet some young and upcoming Iwa ninja trainees. They might be curious about Naruto and his abilities from Konoha. These trainees could either look up to Naruto or be jealous of his fame, leading to various interactions. Also, there could be some old - timer Iwa ninjas who remember past events involving Konoha and have their own views on Naruto's presence in Iwa.
Another way is that he forms an unexpected alliance within Iwa. There could be a dissident group in Iwa who oppose the capture of Naruto. They might help him escape in exchange for some future favor or because they believe in Naruto's cause. Naruto has a way of inspiring people, even those who are initially his enemies, so this is a plausible scenario.
One possible reason could be a threat to Konoha. If Iwa planned an attack on Konoha, Naruto, as a defender of his village, might take the fight to them and end up destroying parts of Iwa in the process.
Well, he might face a lot of challenges. The people in Iwa could be initially hostile as he's from Konoha. He'd have to prove himself. Maybe he'd learn new jutsu unique to Iwa's style.
Well, Naruto might face a lot of challenges in Iwa. He could encounter new types of jutsu that are unique to Iwa ninjas. Maybe he'll make some new friends or foes there.