Add a field to the Arrow class and give it a different value for each arrow (when created). Then when clicked, you can do whatever depending on the value of the field. Or, assign and keep a reference to each one in your world class (which would give each one a different name) as you create them and have the world check for clicks on each one.

Sorry for my late reply. I actually found one of your previous posts and got it to work (in between the time that greenfoot takes to check its not spam) but thank you very much :) I used getWorld().getObjecta().get() to specify the specific object.