How to convert raw data to angular data to display on serial plotter?

Using accelerometer (g) unit to be converted to degree/second

#include "CurieIMU.h"

void setup() {
  Serial.begin(9600); // initialize Serial communication
  while (!Serial);    // wait for the serial port to open

  // initialize device
  CurieIMU.begin();

  // Set the accelerometer range
  CurieIMU.setAccelerometerRange(2);

}  

void loop() {
  float ax, ay, az; //scaled accelerometer values

  // read accelerometer measurements from device, scaled to the configured range
  CurieIMU.readAccelerometerScaled(ax, ay, az);

  
  Serial.print(ax);
  Serial.print(',');
  Serial.print(ay);
  Serial.print(',');
  Serial.print(az);
  Serial.println();
}

atan2().

What is the atan2() for?

Have you looked at the examples that come with the CurieIMU library?