Would you like help identifying your specific MXTronics model? If so, describe the board (number of pins, button labels, any text on the main chip).
MXTronics is a brand that produces various electronic modules (like MP3 players, voice boards, and Arduino shields). The exact process depends on which specific MXTronics product you have (e.g., a DFPlayer Mini clone, a voice sound board, or a serial MP3 module). mxtronics sd card firmware download