He might be shocked by the advanced technology. There could be new forms of ninjutsu or combat styles. He would also have to adapt to a different social structure.
In a 'Naruto sent to hell' fanfiction, it could be that Naruto is sent to hell as part of a test. The gods or some powerful entities want to see if he can bring hope and change to the damned souls in hell. So, Naruto starts to teach the souls in hell about friendship, perseverance and the ninja way. He tries to reform the place from within, facing many challenges along the way like powerful hell guards and the dark energy that tries to corrupt him.
In some fanfictions where Naruto is sent to hell, he might face various challenges. He could encounter powerful demons who want to harm him. But Naruto, being a strong - willed character, would likely try to fight his way out. He might also meet some other lost souls in hell and try to help them while finding a way back to the living world.
Well, Naruto would likely bring his sense of determination and never - give - up attitude to Earthland. In Earthland, which has its own set of power systems and magic, Naruto could start to learn and combine his ninja skills with local magic. He might form new friendships with local mages, and together they could face challenges that neither could have faced alone. For example, he could help in fighting against some dark guilds that are causing chaos in the land.
In some fanfictions, if Naruto was sent to the Third Shinobi War, he could change the course of many battles. His unique jutsus like the Rasengan might surprise the enemies. He could also inspire his comrades with his never - give - up attitude.
In a fanfic where Naruto is sent to Haven, he might find himself in a very different environment compared to Konoha. He could encounter new types of magic or powers that are unique to Haven. Naruto's strong will and determination would likely lead him to adapt quickly and try to find a way to use his skills to help the people there. Maybe he would form new alliances and friendships with the inhabitants of Haven.
Well, if Naruto were sent to Hogwarts in fanfiction, it would be quite an adventure. His chakra control could potentially interact in interesting ways with magic. He might make friends with Harry Potter and his gang. His rasengan could be seen as a very strange and powerful spell - like thing in the wizarding world. And he'd surely bring a new kind of energy and chaos to Hogwarts.
Ruby could be a potential ally. She is brave and has a strong sense of justice, just like Naruto. They could team up and use their unique abilities to fight against the Grimm. Another one could be Jaune. He is a bit of an underdog, and Naruto has a soft spot for those kinds of characters. He could help Jaune improve his skills.
Definitely Pikachu. Since Naruto is often in need of a quick and agile ally, Pikachu's speed and electric attacks would be very useful. Plus, Pikachu's cute appearance but powerful abilities would create an interesting contrast with Naruto's ninja style.
Naruto would probably choose a Pikachu first. Pikachu is energetic and has a lot of spunk, just like Naruto. They would both be full of enthusiasm and would make a great team right from the start.