SD Card - Auto Index File Name to next available file

I am trying to auto index an SD card file name by using the next available. I want to start with “1.csv” and if that already exists use “2.csv” and so on until I find the next unused file name. Then use that file name in my write to SD data logger. I am getting an error with the code bellow. It looks like I can not use a variable as a parameter.

Error is:
“no matching function for call to ‘SDClass::exists(String&)’”

Any suggestions on how to accomplish this? Thanks!

#include <i2cmaster.h>
#include <SD.h>

//Set by default for the SD Card Library
//MOSI = Pin 11
//MISO = Pin 12
//SCLK = PIN 13
//We always need to set the CS Pin
int CS_pin = 10;
int pow_pin = 8;
unsigned long time;
int file = 0;
String fileString;

void setup()
{
	Serial.begin(9600);
	Serial.println("Setup...");
	
        //CS Pin is an output
        pinMode(CS_pin, OUTPUT);
        
        if (!SD.begin(CS_pin))
        {
          Serial.println("Card Failure");
          return;
        }
        Serial.println("Card Ready");
        
        
       fileString = (String(file) +".csv");
        while (SD.exists(fileString));
        {
          file = file + 1;
          fileString = (String(file) +".csv");
        }

I finally got it to work! I found some older example in the forum and was able to adapt them to work. Here is my code for reference.

PS: please excuse my sloppy coding. I am new to text based coding.

#include <i2cmaster.h>
#include <SD.h>

//Set by default for the SD Card Library
//MOSI = Pin 11
//MISO = Pin 12
//SCLK = PIN 13
//We always need to set the CS Pin
int CS_pin = 10;
int pow_pin = 8;
//float refresh_rate = 0.0;
unsigned long time;
int file = 0;
char fileString[12];


void setup()
{
	Serial.begin(9600);
	Serial.println("Setup...");
	
        //CS Pin is an output
        pinMode(CS_pin, OUTPUT);
        
        if (!SD.begin(CS_pin))
        {
          Serial.println("Card Failure");
          return;
        }
        Serial.println("Card Ready");
        
        
        
        
     sprintf(fileString, "%02d.csv", file);
    
      do
        {
         file = file + 1;
         sprintf(fileString, "%02d.csv", file);
        } while (SD.exists(fileString));
        
      Serial.println(fileString);