Hi, I lost my replacement iPhone5 for 3 months ago

And I didn't keep the replacement package(As I thought my phone will be gone forever), at the same time I re-installed my Windows7(So no backup file kept). The problem here is the police called me and said they find my iPhone and they need the IMEI no. of the phone for confirming that is mine. How can I find the IMEI no. only with the original package of my iPhone5?