It is .pes format..and I have read that you have to have the Bernina software to convert to .art. There are a number of free format changing programs, but I've not seen the .art format on any of them. I use
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http://www.wingssystems.com/index.php/products/myeditor/ my editor, and </cite>
Convert Embroidery formats with Tajima Pulse Ambassador FREE ... but neither of my programs have conversion to .art I hope you find some help from someone with the Bernina software.