Pe casieră o întreb dacă pot plăti cu cardul aici, nu cu numerar.

Because casieră is a direct object referring to a person. In Romanian, direct objects that are specific people often take pe.

So:

• întreb casiera = I ask the cashier
• pe casieră o întreb = the cashier, I ask her / it is the cashier that I ask

This pe does not mean on here. It is a grammatical marker for a personal direct object.

This is a very common Romanian pattern called clitic doubling.

• o = her
• pe casieră = the cashier

Romanian often uses both together when the direct object is a specific person, especially when that object comes before the verb.

So:

• O întreb pe casieră = I ask the cashier
• Pe casieră o întreb = The cashier, I ask her

In English, this looks redundant, but in Romanian it is normal.

Putting pe casieră first gives it emphasis or makes it the topic of the sentence.

Compare:

• O întreb pe casieră... = neutral word order
• Pe casieră o întreb... = As for the cashier, I ask her... / It’s the cashier that I ask...

So the fronted object highlights who is being asked.

Both can appear in Romanian, but they are not exactly the same form.

• casieră = an indefinite form, basically cashier
• casiera = the cashier

In a structure with pe and clitic doubling, Romanian can use the noun without the article in some contexts, especially in less formal or more streamlined speech. However, many learners will first meet the more clearly definite version:

• Pe casieră o întreb...
• Pe casiera o întreb...

In practice, you will very often hear and see Pe casieră o întreb as a natural sentence meaning I ask the cashier.

Here dacă means if / whether.

It introduces an indirect yes-no question:

• întreb dacă pot plăti... = I ask if I can pay...

Do not confuse this with English if in conditional sentences only. Romanian dacă is used both for:

• if in conditions
• if / whether in indirect questions

Here it is the second use.

After a putea (can / to be able to), Romanian commonly uses the infinitive:

• pot plăti = I can pay

This is the normal standard structure.

You may also hear other verb patterns with să, but after a putea, the infinitive is the usual choice. So in this sentence, pot plăti is exactly what you should expect.

This is about idiomatic usage.

• cu cardul = by card
• cu numerar = in cash / with cash

Romanian often uses the definite article in expressions like cu cardul, cu telefonul, etc., where English would not necessarily use the.

But numerar often behaves more like a mass noun or an adverbial expression in this context, so cu numerar is the usual phrase.

So you should learn them as set expressions:

• a plăti cu cardul
• a plăti cu numerar

Usually, cu cardul is the normal and idiomatic expression for by card.

cu card may appear in some contexts, but it often sounds less standard or less natural for this meaning. For everyday speech about payment method, cu cardul is what you should use.

Aici means here, and in this sentence it refers to this place / this store / this checkout / this establishment.

So the speaker is asking whether card payment is possible here, in this location.

It is not attached only to cardul. It applies to the whole idea:

• Can I pay by card here...?

Because Romanian, like English, often omits repeated words when they are understood.

Full version:

• ...dacă pot plăti cu cardul aici, nu dacă pot plăti cu numerar.

But that sounds repetitive. So Romanian shortens it to:

• ...cu cardul aici, nu cu numerar.

This is a contrast:

• by card, not in cash

So nu cu numerar is an elliptical expression, not a complete clause.

It mainly marks a contrast between two options:

• with card
• not with cash

Depending on context, it can imply either:

1. the speaker wants to know whether card is accepted rather than cash, or
2. the speaker specifically intends to pay by card, not cash

So the grammar gives a contrast; the exact practical meaning depends on the situation.

It is understandable and natural, but it has a bit of emphasis because the object comes first.

A more neutral version would be:

• O întreb pe casieră dacă pot plăti cu cardul aici, nu cu numerar.

Or even more simply in everyday speech:

• Întreb casiera dacă pot plăti cu cardul, nu cu numerar.

So the original sentence is fine, but it is not the most neutral word order.

Romanian often uses the present tense for an action happening right now:

• întreb = I ask / I am asking

So here it means something like:

• I ask the cashier whether I can pay...

It is just the ordinary present tense, used for a current action.

Because casieră is a feminine noun referring to a woman, so the direct-object clitic is o.

Romanian clitics agree with grammatical gender and number:

• îl = him / it (masculine singular)
• o = her / it (feminine singular)
• îi / le, etc. for other patterns

Here, since casieră is feminine singular, o is the correct form.

Not with the same meaning.

• pe casieră marks the cashier as the direct object: she is the person being asked
• la casieră usually means at the cashier / at the checkout / to the cashier’s place

So:

• Pe casieră o întreb = I ask the cashier
• La casieră întreb = I ask at the cashier’s desk / at the checkout

They are different structures.

The main dictionary forms are:

• casieră → noun, cashier (female)
• a întreba → to ask
• a putea → to be able to / can
• a plăti → to pay
• card → card
• numerar → cash
• aici → here
• dacă → if / whether

This is useful because several words in the sentence are inflected:

• întreb comes from a întreba
• pot comes from a putea
• cardul comes from card with the definite article attached