you had a lot of errors in your code,i fixed most of them.

Code:
#include<stdio.h>
#include<math.h>
#include<conio.h>
#include <stdlib.h>
#include<string.h>

void student_db();
void disp_info();
void edit_info();

struct s_database{
    char s_name[10];
    char s_ph_number[10];
    char s_ID_number[10];
}database[10];

int countStudents=0;
int main(){
    char num;
    while(1){
        printf("Enter 1-> To create New Student\nEnter 2-> To Display Information of all students\nEnter 3-> To Edit Students Info\n");
        fflush(stdin);
        scanf("%d",&num);
//num=0; //num=0 should be initialized here because if not than switch will be executed twice.
        switch(num){
            case 1:{
                student_db();
                break;
            }
            case 2:{
                disp_info();
                break;
            }
            case 3:{
                edit_info();
                break;
            }
            case 4:{
                exit(1);
            }
            default:{
                printf("Invalid number entered...please select 1,2 or 3\n");
// num=0; //num=0 should be initialized here because if not than switch will be executed twice.
                break;
                getch();
            }
        }
    }
    //getch();
    return 0;
}


void student_db(){
    int no=0;
    countStudents=0;
    int error=1;
    int i=1;
    while(error==1){
        error=0;
        printf("--------------------------------------------------------------------------------\n");
        printf("Enter the number of students information you will be adding to the database\n");
        fflush(stdin);
        scanf("%d",&no);
        printf("--------------------------------------------------------------------------------\n");
        if(no>0){
            printf("Enter students name\t\tcontact number\t\tID_number\n");
            while(no!=0){
                countStudents++;
                printf("Enter student[%d] Information\n",i);
                fflush(stdin);
                gets(database[i-1].s_name);
                fflush(stdin);
                gets(database[i-1].s_ph_number);
                fflush(stdin);
                gets(database[i-1].s_ID_number);
                // fflush(stdin);
                no--;
                i++;
            }
            printf("Student Info saved \n");
            
            getch();
            //student_db();
        }else{
            printf("Invalid number entered...\n");
            error=1;
        }
        //goto step1;
        //student_db();
    }
}

void disp_info(){
    int no;
    for(no=0;no<countStudents;no++){
        puts(database[no].s_name);
        puts(database[no].s_ph_number);
        puts(database[no].s_ID_number);
    }
}

void edit_info(){
    char name[10],no;
    int found=0;
    printf("enter the students name to edit his database\n");
    //getch();
    fflush(stdin);
    gets(name);
    for(no=0;no<countStudents;no++){
        if(strcmp(database[no].s_name,name)==0){
            printf("Enter students name\t contact number\t and ID_number\n");
            gets(database[no].s_name);
            gets(database[no].s_ph_number);
            gets(database[no].s_ID_number);
            found=1;
        }
    }
    if (found==0) printf("entered name is not in the student database list\n");
}
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