Error Message: link to console.log TypeError: Cannot read properties of undefined (reading 'toString')

I'm trying to convert a image buffer to longtext in order to store it in mysql. Using multer as the middleware.

//HTML: link to html code

<div id="container">
     <form id="upload-images-form">
          <input id="image-upload" type="file" value="Upload Image" accept="image/png, image/gif, 
          image/jpg, image/jpeg" multiple="multiple"/>
          <input id="submit" type="submit" value="Submit"/>
     </form>
</div>

//server.js: link to server code

app.post('/upload-images', upload.array("files"), function (req, res) {
     console.log(req.files);
     var image = req.files.buffer.toString('base64')
     console.log(image);
});