The IMEI that you need is the one that has 15 digits. Also you need your s/n, and you need a valid email (it can be gmail, outlook, etc...). You need to enter the captcha numbers that appears below (it has time limit, so if it throws you an error message, refresh it).
Also, important to mention. It's better not to have modified the phone, i'm talking about modifications that could alter the IMEI. Until know that only modification could be installing the CN ROM instead of the ROW ROM. And its a probability, it's an advice that the seller gave me.
So you are a 4pda forum member, I too. So could you gave them this recommendation for me please. I bought the phone from SUNSKY, the 4/64 GB version. It only took 1 labor week to be in my house. I'm from Mexico, so the distance were big, but this seller ships fast. I choose the dhl express option, by recommendation of the seller.