Download File in Specified folder [Javascript]

Question

I've been creating a small project with the aim of downloading youtube videos on my server. in theory it already works, but I want that, when I press download, it downloads the file in a specific folder inside the server.

this is my code for the function.

Used library: ytdl-core

app.get("/download", async(req, res) => {
    const info = await req.query.url;
    const v_id = info.split('v=')[1];
    res.header("Content-Disposition", `attachment; filename="${v_id}.mp3`);
    ytdl(info, {format: 'mp3'}).pipe(res);
});