It gives an error when sending a post request, I want to send files, but it gives an error "["validation.array"]". How to solve it?

Question

JavaScript

I write code in vue js

And here is the task, you need to send files to the server "user message, lesson id, and file". An error occurs when sending a file, because an array needs to be sent to the server, but the question is how?
I created an array separately and tried to push it there, and then send this array to the server, but I still can’t do it ...

Here is the construction itself in html


and here is the code


itself herself