If I can't figure out how to get the required serial number

Apple for some reason requires serial numbers not imei numbers. I no longer have the phones and can't figure out how to get the serial numbers, although I do have the IMEI numbers. Why doesn't Apple require either or (serial or IMEI #) As it is, probably very few people have kept this old information on file, who knew we'd need it? It's convenient for Apple because their payout therefore will be a quarter of what they owe, since no one can find the required serial number.

I tried contacting Apple, looking it up on their website - only one device is listed on their site, my family has had multiple 6s and 7s....

If I can't figure out how to get the required serial number, I need to be able to write and complain to the appropriate parties. This is not acceptable!

[Re-Titled by Moderator]