Does Cé acu? mean "Which of them"?

How would you say in Irish:

Customer: I like that car.
Salesperson: Which one?

or

Customer: I like those dresses.
Salesperson: Which ones?

Could the salesperson have said Cé acu? in both cases?

More like just "which?"

In both these cases, you can just answer cé acu "Which?"

For the first you could also say:
Cé acu carr ? "Which car?"
Cé acu é ? "Which is it?"
Cé acu carr é ? "Which car is it?"
Cé acu ceann é ? "Which one is it?"

For the second:
Cé acu gúnaí? "Which dresses?"
Cé acu iad ? "Which are they?"
Cé acu gúnaí iad? "Which dresses are they?"
Cé acu cinn iad ? "Which ones are they?"

You might also be able to say just cé acu ceann ? "which one?" and cé acu cinn ? "which ones?".

You could also avoid acu and just say Cén carr (atá i gceist agat) ? "What/which car (do you mean)?" or Cé na gúnaí ? "What/which dresses?".

Await confirmation or correction ...

_________________
Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

Cé acu acu? – Which one?

What Breandán said is correct

But just to add- when I say "acu(b)" I'd be choosing from a particular selection. Like you said "which of them?".
There is a subtle difference between "cé acu?" and "cén ceann?"

_________________
___________________________________________________________

It is recommended that you always wait for three to agree on a translation.
I speak Connemara Irish, and my input will often reflect that.
I will do an mp3 file on request for short translations.
___________________________________________________________