Learn Italian: Ognuno cerca un carrello nel reparto, ma non ce ne sono più. - Everyone looks for a cart in the department, but there are no more of them.

It is a combination of the pronoun ci (there) and the partitive pronoun ne (of them). Whenever ci is followed by ne, its i changes to an e, giving us ce ne. Together with sono, the phrase ce ne sono means "there are (some) of them".

Why does the sentence end with the plural verb sono when it started with the singular Ognuno cerca?

The first half is about ognuno (everyone or each person), which takes a singular verb. But in the second half, the verb sono refers to the carts. Because ne stands in for "of them" (the carts), the verb must be plural to match: non ce ne sono più (there are no more of them).

Why use ognuno instead of tutti to say "everyone"?

Ognuno specifically means "each one" or "every single person," and it always takes a third-person singular verb like cerca. You could use tutti, but because it means "all people," you would have to change the verb to plural: tutti cercano. Both are perfectly natural here.

Why is there no Italian word for "for" after cerca?