In Aadhar Card Unique ID process first step is go to -> enrollment centers
here on center you will submit your id proof and enrollment offcer will submit your aadhar request form.
And after fill this request form you will receive your acknowledgement slip. On this slip you can see your enrollment number like: 1234/12345/12345 and date and time 10/12/2014 12:40:57
This enrollment number and date time combination is your enrollment number for Check Aadhaar Card Status