How to find the index of an element in an array, vector or slice in Rust?

Hello! I'm new to Rust and trying to solve a simple problem: find the index of an element in an array. In other languages (e.g., Python), I'm used to methods like `list.index()`, but in Rust it's different. Here's an example: I have an array of numbers, and I want to find the index of the number `5`. ```rust fn main() { let arr = [1, 3, 5, 7, 9]; let target = 5; // How to find the index of 5? } ``` I tried using `arr.iter().position(|x| x == target)`, but I get an error. The documentation says that `position` returns `Option`, and I don't understand how to properly handle this result. Also, I'm not sure if this works for `Vec` and slices (`&[i32]`). Another question: what to do if the element is not found? In Python, I would get an exception, but in Rust, as I understand, I need to handle `None`. But how do I do this?