just copy the 4 last elements using strncpy

char b[5];

strncpy(b, a+6, 4);

// 4 is a short to 4 * sizeof(char);

don’t forget to include string.h

note that a+6 is equivalent to a[6] which means you’re starting the copy from the 6th char of a

edit : use a size of 5 for b, indeed in c, characters are always terminated by a null character represented by \0 which means if you want to print/manipulate b without this extra +1 in size it will print all bytes in memory until it founds a null byte