How do you spell Tommy in Chinese?

You don't 'spell' your name in Chinese , you find syllables that match the sound of your name and you try to find ones that sound nice

塔 沚 Ta me , sounds similar to Tommy , means Tower Island

or

绦蜜 Tao mi , which means Silk - Sweet

or

simply

禢 祢 Tao Mi , which is just two names. This would be the safest to use I guess