How to send temperature data using GSM SIM900 Module to Node-RED

please how to send temperature data to node red using sim900 gsm module via mqtt .

i have installed mosquitto broker and node red in my raspberry pi .

my system is DHT11 sensor + Arduino+ nodered

What is node-red running on and how is it connected to the Arduino?

node red is running in raspberry pi
i want send data using sim900 via mqtt to nodered

MQTT requires a broker so Nodered will need to point at whatever broker you use.

Your arduino with GSM will need to send the data to the MQTT broker. How you do that isn’t anything to with Node-red

i used mosquitto broker which is installed on raspberry pi
node red is installed too in the same raspberry pi
i need code arduino to send data usino gsm sim900 to the broker in nodered

This forum is dedicated to Node-RED.
If you want help with Arduino code to send data to a MQTT broker then you are better asking on a forum about arduino.

If you are using the same pi for your broker and Node-RED. The machine will probably need to be visible from the internet. Before you put the pi onto the internet you HAVE to make sure it is secure and that includes Node-RED. If you search this forum you will find many topics with suggestions about what to do.