Bulletinboard/app/Models/File.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class File extends Model
{
    use HasFactory;

    protected $fillable = [
      "link"
    ];

    public  function  post(){
        return $this->belongsTo(Post::class);
    }
}