Why not just use sscanf? This supports a ton of destination types and also error handling:

#include <stdio.h>

int main() {
    const char *str = "12345";
    unsigned int value;
    
    if (sscanf(str, "%u", &value) == 1) {
        printf("The converted unsigned integer is: %u\n", value);
    } else {
        puts("Conversion failed.");
    }
    
    return 0;
}