Kinsman,

Of course you're a MacMillan-- as our clan genealogist has pointed out, your name is another form of Baxter. According to our Chief, George Macmillan of Macmillan and Knap, there are three authorized MacMillan tartans: Dress MacMillan, Ancient MacMillan, and MacMillan Hunting. These are available in modern, ancient, and weathered colours, and you are free to wear whichever tartan or colour you choose.

Welcome aboard!