Use data on SD card for controlling a servomotor

Other Hardware Storage
3

here is my program

the values I had in my SD card scrolls well in the serial monitor, but I don't know hw to use them to move my servomotor.

#include <SdFat.h>
#include <SdFatUtil.h> 
#include <ctype.h>

#include <Servo.h> 
 
Servo myservo;

Sd2Card card;
SdVolume volume;
SdFile root;
SdFile file;

char name[] = "Test.txt";    
char contents[256];           
char in_char=0;
int index=0;  
                
void setup(void)
{  
    Serial.begin(115200); 
    myservo.attach(9);       
    pinMode(10, OUTPUT);     
    card.init();               
    volume.init(card);        
    root.openRoot(volume);     
}


void loop(void){    
    
    file.open(root, name, O_READ);    
    in_char=file.read();              
    
    while(in_char >=0)
       {           
        Serial.print(in_char);    
        in_char=file.read();    
       }
    file.close();    
    delay(1000);     
}