Need Help With Code

I need some help with my project. Im reading a accelerometer with ADC on port PA0 on a Atmega16. Im reading only X-axes. I want to add Y and Z also, but I dont know how.
Im reading the input with TeraTerm, line by line downwards. I want the y and Z to be added on the side of the X value.
IM using AVR studio 4.

Can anyone help me with thsis?

Code:

#include<avr/io.h> 
#include<util/delay.h> 
#include<avr/interrupt.h> 


#define LONGOUT 7 
char buffer[LONGOUT];

void adc_init(void); 
unsigned int adc_read(void); 
void adc_conversion(uint16_t); 




// ADC configuration 
void ADC_init(void) { 
  ADMUX=(1<<REFS0); 
  ADCSRA=(1<<ADEN)|(7<<ADPS0); 
} 

uint16_t ADC_get_reading(void) { 
  ADCSRA |= (1<<ADSC); 
  while(ADCSRA & (1<<ADSC)); 
  return ADC; 
} 

uint16_t ADC_read(void) { 
  uint8_t i; 
  uint16_t retval = 0; 
  ADC_get_reading(); // dummy read - just discarded 
  for (i=0; i<8; i++) { 
    retval += ADC_get_reading(); 
  } 
  return retval / 8; 
} 


void init_UART(void)
{
	UCSRB = ((1 << RXCIE) | (1 << RXEN) | (1 << TXEN)); 
    UCSRC = ((1 << UCSZ1) | (1 << UCSZ0)); 
    //Baud rate till 19200.  
    UBRRL = 25; 
    UBRRH = 0; 
}


void uart_sendchar(char c) { 
   while(!(UCSRA & (1<<UDRE))); 
   UDR = c; 
} 

void uart_printstring(char * str) { 
  while (*str) { 
   uart_sendchar(*str++); 
  } 
} 


void main(void) {
	
 DDRC = 0x00;	
 init_UART(); 
 ADC_init();
 
 
  while(1)
  {
	 if (PINC & 0x01) //If PortC pin 0 is True, program stops.
	{ 
 ADC_read(); 
 char buffer[8]; 
 itoa(ADC, buffer, 10); 
 uart_printstring(buffer);
 uart_printstring("\r\n"); 
 _delay_ms(1500); 
    } 
  }
}