how to access a character in an array of strings in c

I have been trying to uppercase the first letter of a string which is inside an array of strings I tried a lot of methods but none of them worked here is my code:

 #include <stdio.h>
 #include <stdlib.h>
 int nw=0;
 char words[30][50];
 int main(){
 printf("enter your words when you finish write b\n");
 do{
 nw++;
 scanf("%s",&words[nw]);
 }while(strcmp(&words[nw],"b")!=0);
 printf("%s",toupper(&words[1][0]));
 }

what should I do please help

For starters you need to include headers <ctype.h> and <string.h>

#include <ctype.h>
#include <string.h>

There is no great sense to declare these variables

int nw=0;
char words[30][50];

in the file scope. They could be declared in main.

Instead of this call

scanf("%s",&words[nw]);

you have to write at least

scanf("%s", words[nw]);

The condition in the do-while statement should look like

while( nw < 30 && strcmp(words[nw],"b") != 0 );

And instead of this call'

printf("%s",toupper(&words[1][0]));

you should write

words[1][0] = toupper( ( unsigned char )words[1][0] );
printf( "%s", words[1] );

Here is a demonstrative program.

#include <stdio.h>
#include <ctype.h>

int main(void) 
{
    char words[30][50] =
    {
        "hello", "world!"
    };
    
    for ( size_t i = 0; words[i][0] != '\0'; i++ )
    {
        words[i][0] = toupper( ( unsigned char )words[i][0] );
        printf( "%s ", words[i] );
    }
    putchar( '\n' );
    
    return 0;
}

The program output is

Hello World!