I'm probably not the one to answer this, as I once hired someone with purple hair and goth makeup, in a fairly conservative company. But she was definitely the right person for the job and was a fantastic employee.
My take, after having done a fair bit of interviewing and hiring, is that a job candidate should be clean and neat and appropriately dressed. I would only notice earrings if they stood out from the rest of the outfit or were so over the top that they couldn't be missed.
What type of company will you be interviewing with? For Hot Topics, say, four earrings would be a bonus, for example. For a bank, I'd go with simple stud earrings, one per ear.
And I don't think you have to stick with stud earrings, if you don't want to. It can be nice to see a tiny bit of a candidate's personality in their choice of accessories. If the copper hoops work with the rest of your outfit, i.e., they blend in instead of sticking out, I don't see why you can't wear them. If you are going to be wearing a navy blue skirt suit with pantyhose and heels, then maybe you need the little pearl studs. But if you are wearing a more business casual outfit, then hoops aren't inappropriate.
I've interviewed over 100 people. There are only two candidates who stand out because of what they wore. The young woman in the wrinkled, faded brown knit skirt and faded black knit top which kept showing her grungy bra straps, with uncombed hair with a scraggly part in it--she just looked like she didn't care about herself or anything else. (Her resume which showed 13 jobs in 2 years didn't help, either.) Remove the wrinkles and comb the hair, at least. I won't fault someone who can't afford better clothes, but they should be clean and neat at the very least. And undergarments should be concealed.
And the woman who showed up in a brightly colored floral sundress, with a tiny, pretty little handbag, strappy, high heeled sandals and her resume in a manila envelope--she was dressed for a garden party, not work. It wasn't a bad outfit, but it did not send any signals that she knew how to dress for an office. The manila envelope by itself wasn't an issue, but combined with all the other signs, it didn't read, "I'm here and I'm ready to work."