I try to use this, but not work, style not changed

pandoc -f markdown -t markdown -o string.h.md.out string.h.md

the following is a code block, how can I convert it to ``` style

    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    int main (int argc, char const *argc[]){
        char s[] = "hello";
        char *p = strchr (s, 'l');
        char c =*p;
        *p ='\d';
        char *t = (char*)malloc(strlen(p)+1);
        strcpy(t,p);
        printf("%s\n",t);
        free(t);
       
        return 0;
    }