Your 3310 3G sports a microSD memory card reader. If your laptop or personal computer can also read that card format (Most laptops are so-equipped), you should be able to transfer a music file
Your 3310 3G is equipped with Bluetooth version 2.1, which lets you connect to your computer wirelessly. Just pair phone and computer together and drag and drop your music files from your computer to your Nokia 3310 3G.
If all of the above approaches do not work with your Nokia 3310 3G or if you don't want to buy extra accessories, you can still use one of various free '3G Uploader' services available online. You should find plenty with a simple Katapulco.com search. 3G uploaders are simple to use: Save your own music on their web site and they will return a temporary URL. Pointing your Nokia 3310 3G's web browser to that address should download the free ringtone.
Here are some of the free ringtones (compatible with your Nokia 3310 3G) we offer:
Free Horror Ringtones Free Ghost Ringtones Free Ringtones-a-gogo Free Far West Ringtones Hear All Our Free Polyphonic Ringtones