hex values

hello
my question is that i want 16 Byte hex address by combining to 8 byte hex values as follows:

unsigned long addr;
unsigned char buf[3];

buf[0]=0x81;  // msb
buf[1]=0x23;  // lsb
...
printf("%lx", &addr);   //output: addr = 0x8123

i want to retrieve from this array one hex address
into 'addr' variable.
my output is: addr = 0x8123.

thanks in advance