A polícia vai localizar o pertence.

A polícia means the police as an institution or force. In Portuguese, polícia is a singular noun, even though it refers to a group of people.

So:

• A polícia vai localizar... = The police will locate...
• Os policiais vão localizar... = The police officers will locate...

Both are possible, but they focus on slightly different things:

• a polícia = the police as an organization
• os policiais = the individual officers

Because the subject is a polícia, and polícia is grammatically singular.

This is similar to how some collective nouns work in English. Even if many people are involved, Portuguese usually matches the verb to the grammatical form of the noun.

So:

• A polícia vai localizar... = singular subject, singular verb
• Os policiais vão localizar... = plural subject, plural verb

Vai localizar is the very common ir + infinitive future, which works a lot like going to + verb in English, but in Portuguese it is also widely used for plain future meaning.

So these are both possible:

• A polícia vai localizar o pertence.
• A polícia localizará o pertence.

In Brazilian Portuguese, vai localizar sounds more natural and conversational in many situations.
Localizará is correct too, but it is usually more formal or written.

Here, pertence is a noun meaning something like belonging, possession, or personal item.

However, this is the part of the sentence that may sound a little unusual to a Brazilian speaker. The singular pertence exists, but in real everyday use, pertences in the plural is much more common:

• os pertences = belongings

If you mean one specific object, Brazilians might more naturally say:

• o objeto
• o item
• o bem in some formal contexts

So grammatically, o pertence is possible, but stylistically it may sound less natural than other choices.

Yes. Pertence can also be the he/she/it belongs form of the verb pertencer.

For example:

• Isso pertence à Maria. = That belongs to Maria.

So pertence can be:

• a noun: a belonging / an item
• a verb form: belongs

In your sentence, it is clearly a noun because of the article o:

• o pertence = the belonging / the item

That article makes it clear that pertence is not being used as a verb here.

O is the masculine singular definite article, meaning the.

So:

• o pertence = the belonging / the item
• um pertence = a belonging / an item

Portuguese uses articles very often, sometimes more often than English does. Here, o shows that we are talking about a specific item, not just any item.

They are close, but not exactly the same.

• localizar = to locate, to determine where something is
• encontrar = to find

Localizar can sound a bit more official, technical, or procedural. That makes it a reasonable choice with a polícia.

For example:

• A polícia localizou o suspeito. = The police located the suspect.
• Encontrei minhas chaves. = I found my keys.

So in a police context, localizar sounds quite natural. The less natural part of the sentence is more likely o pertence, not localizar.

It is mostly grammatical, but not fully natural-sounding because of o pertence.

A Brazilian speaker would probably say something more like:

• A polícia vai localizar o objeto.
• A polícia vai localizar o item.
• A polícia vai encontrar o objeto.
• A polícia vai localizar os pertences. if you mean the belongings

So the structure A polícia vai localizar... is fine and natural. The main thing learners should notice is that pertence in the singular is uncommon in everyday speech.

A rough pronunciation guide is:

ah poh-LEE-see-ah vai lo-kah-lee-ZAR oo pehr-TEN-chee

A few helpful notes:

• polícia is stressed on cí: po-LÍ-ci-a
• localizar is stressed on the last syllable: locali-ZAR
• pertence is stressed on ten: per-TEN-ce

In connected Brazilian speech, some sounds may get smoother and less separated than this guide suggests, but the stress pattern above is the important part to learn.