Solution:
$path_array = wp_upload_dir();
$path = str_replace('\\', '/', $path_array['path']);
$target_path_sia = uniqid().$_FILES["file"]["name"];
move_uploaded_file($_FILES["file"]["tmp_name"],$path. "/" . $target_path_sia);
echo "Stored in: " . $path. "/" .$target_path_sia;