How to send hex to child over mqtt with nodered

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Hello Im new here and Im learning and I would like to ask you, how I can send sometin like this “0x15 0A c9 84 02 6b 01 98 fa” to my children, WisGate Developer D0 / D0+ thats my gateway.
I would like to do it over nodered can you help me with that ?
there is Im node-red

image
image1069×517 29.5 KB

what the name of topic a need to use ?
and here is my function

msg.payload = msg.payload.split(" ");
var result = [];
msg.payload.forEach(str => {
 result.push(parseInt(str,16));  //hex base-16
})
msg.payload = new Buffer(result);
return msg