# [Vyxal](https://github.com/Vyxal/Vyxal), 8 bytes
```
ṘKRṘ=ƛTh
```
[Try it Online!](https://vyxal.pythonanywhere.com/#WyIiLCIiLCLhuZhLUuG5mD3Gm1RoIiwiIiwiW1wiQVwiLFwiQlwiLFwiQ1wiLFwiQVwiLFwiQVwiXVxuXCJBXCIiXQ==)

```
ṘKRṘ     # Over suffixes...
    =    # Check if each value is equal to the second input
     ƛ   # Map...
      Th # Find the first index where it is equal
```