This service convert you serial in imei.
if you haven't imei, you can use this service for know his.
If you have IPad without Sim, IPod, Iwatch - you can't find imei, bcz don't have sim card.
If you want to check a more 1 serial - enter all the imei in a column and specify the number in the corresponding field.
||You can get IMEI, if you have only serial number (Support only IPhone and IPad + cellular)