Shiftout Module

Hi 
  my two shiftout modules have just arrived and I wanted to try them out .

I did a search on this forum and found a post on how to use 2 modules together to shift 16 bits.
https://www.dfrobot.com/forum/index.php? ... 112#msg112

The above search result contained ...
#define SCLK 35    // (1) DFR0072 ShiftOut SCLK Serial-Clock Input
#define DIN 31    // (5) DFR0072 ShiftOut DIN Serial-Data Input 
#define iCS 33    // (3) DFR0072 ShiftOut /CS Chip-Select Input set low to receive data, set high to output data

I think I understand what the code is doing but am confused by the choice of pin numbers. My arduino doesnt have that many pins so I am guessing he is using the arduino 2560 which has the extra pins. 
Will it be ok to use my Uno instead and can I choose more or less any 3 digital pins for the outputs for
SCLK , DIN and iCS

Regards
Don