iPhone X e-mail contact list?

I got a new iphone X today. It seems the list of e-mail addresses that used to "auto-fill" on my previous iphone (an iphone 5C) is now missing... but I am not sure it is missing. Is there some place to go on the new iphone X to "see" if there is a list of my e-mail addresses? Can you describe the steps I need to do, to view this list or see if it does or does not exist? On my previous iphone 5C, I don't think this list was in my phone contacts... those were just phone numbers for calls and for texts..? I never entered the e-mail addresses on my old iphone, the old iphone just built them (and remembered them) every time I sent an e-mail from my phone or responded to an e-mail which I received on my iphone. Now, on my new iphone X, when I try to send an e-mail to someone who I usually e-mail, it does not auto-fill their e-mail address... so I am assuming that list of email contacts was lost in the transfer?

The Sprint store rep was doing this late in the day, and he kept my old phone to see if I could get a trade-in allowance... And he had to order a wireless charger from another store, that he didn't have in stock, so I am supposed to go back there. So, I am thinking my old phone is still there -- whether there is any data still on it, is unknown. Do I just need to call him and tell him I have lost the e-mail addresses in the transfer? Or is there some way to "see" them or "find" them? Are they hidden somewhere and I don't know where to look? Or is there some "auto-fill" setting I need to find?? Thanks for any help.

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