You've got pomme right, but you don't pronounce the 'n' in pain. The pronunciation of pain is a little more complicated than that, so I would google "how to pronounce pain in french". The closest english word in pronunciation to pain would be "pay", but with a bit more ie sound after the a. Hope that's not confusing.
She is not supposed to pronounce it because it is silent. You know the difference because of the article "les" which is especially obvious as it comes before a word beginning with a vowel, so there is a liaison and the s is sounded as a z. If it was singular, it would be l'éléphant - completely different sound.
"De" is a preposition which can mean of, from, and various others translations in English. But it is also part of the partitive article (de la/du) used in expressions of uncountable quantity. In English, this can be translated as "some," but often it is omitted. So "Je mange du pain" does not mean "I eat of the bread," it means "I eat bread" or "I eat some bread." "Je bois de l'eau" is "I drink water," not "I drink of the water."
So the translation shown in the list is correct in some contexts, but not this one.
Du is a contraction of "de+le."(singular)
Des is a contraction of "de+les." (plural)
Apart from being used to literally mean "of the," they are also used to describe quantity. "Du" is used for an unspecified quantity of a masculine noun ("le pain") that is not countable . "De la" would be used for a feminine noun.
"Des" is used for an unspecified quantity of something that can be counted (masculine or feminine). So if it was carrots that elephants were eating, you would say "Les elephants mangent des carottes."
In English, sometimes we use the word "some" in these cases, but not necessarily.
The plural of elephant is elephants. "There are two elephants in the zoo." A perusal of scholarly articles online shows consistent use of the -s plural form.
"A herd of elephant" is also sometimes encountered, so the group plural also appears to be a possibility, but only in the context of "a herd."
Even there, a Google search of "a herd of elephant" comes up mostly with "a herd of elephants."
In French, "pain" is countable and uncountable.
- "un pain" looks like "une baguette" but it is thicker.
- "un/du pain de campagne", "un/du pain au levain", "le/du pain de seigle"... are all kinds of specialties: http://vincentcatala.fr/en/different-types-of-french-breads/