Nội dung của bưu kiện quốc tế là hàng hóa.

A natural word-by-word breakdown is:

• nội dung = contents, content
• của = of
• bưu kiện = parcel, package
• quốc tế = international
• là = is/are
• hàng hóa = goods, merchandise

So the structure is roughly:

nội dung + của + bưu kiện quốc tế + là + hàng hóa
= The contents of the international package are goods.

Notice that Vietnamese does not use articles like the or an in the same way English does.

Của is a very common word used to show possession or an of relationship.

So:

• nội dung của bưu kiện = the contents of the package
• literally: contents of package

It works a lot like English of in this sentence.

Examples:

• màu của xe = the color of the car
• tên của tôi = my name / the name of me

In everyday Vietnamese, của is sometimes omitted when the relationship is already clear, but in a formal sentence like this, keeping của is very natural.

Vietnamese usually puts the main noun first, then adds extra information after it.

So:

• bưu kiện quốc tế = international package
  • bưu kiện = package
  • quốc tế = international

In English, adjectives usually come before the noun: international package.
In Vietnamese, descriptive words often come after the noun: package international in a very literal sense.

The same thing happens in many noun phrases:

• xe mới = new car
• sách tiếng Việt = Vietnamese book
• công ty quốc tế = international company

Here, quốc tế describes bưu kiện.

So the phrase groups like this:

nội dung / của / bưu kiện quốc tế / là hàng hóa

That means:

• bưu kiện quốc tế = international package
• not nội dung quốc tế = international content

So the sentence is about the contents belonging to an international parcel.

Là is the copula, similar to to be in English.

Here it links:

• nội dung của bưu kiện quốc tế = the contents of the international package
• hàng hóa = goods/merchandise

So:

• X là Y = X is Y

In this sentence:

• Nội dung của bưu kiện quốc tế là hàng hóa
• The contents of the international package are goods

Even though English uses are, Vietnamese still uses là because Vietnamese verbs do not change form for singular/plural.

In some Vietnamese sentences, especially casual ones, là can be omitted. But in this kind of formal, declarative sentence, là is very natural and expected.

Compare:

• Nội dung của bưu kiện quốc tế là hàng hóa.
  This is clear, formal, and standard.

If you remove là, the sentence feels less complete in this context.

Because this sounds like something from a form, customs declaration, or official statement, là is the best choice.

Vietnamese nouns usually do not change form for singular or plural.

So hàng hóa can refer to:

• goods
• merchandise
• cargo items

The exact number is understood from context.

English forces you to choose between singular and plural much more often. Vietnamese usually does not.

Also, hàng hóa is often treated as a mass or collective concept, similar to merchandise in English.

Both can refer to goods, but hàng hóa is more formal and explicit.

• hàng = goods, stuff, merchandise, wares
• hàng hóa = goods, merchandise, commodities

In official or administrative language, hàng hóa is very common. That is why it fits well in a sentence about parcel contents.

For example:

• bán hàng = sell goods / sell things
• vận chuyển hàng hóa = transport goods

So in this sentence, hàng hóa sounds more formal and precise than just hàng.

Nội dung literally means content or contents, depending on context.

In English, when talking about what is inside a package, we often say the contents. That is why contents is a natural translation here.

But Vietnamese does not force that singular/plural distinction the same way English does.

So:

• nội dung bức thư = the content of the letter
• nội dung bưu kiện = the contents of the package

The English translation depends on what sounds natural in context.

Vietnamese classifiers are often used when talking about a specific countable object with a number or demonstrative.

Examples:

• một bưu kiện = one package
• bưu kiện này = this package

But in this sentence, bưu kiện appears inside a possessive phrase:

• nội dung của bưu kiện quốc tế

Since the sentence is not emphasizing counting or pointing to a specific item with this/that/one, no classifier is needed.

That is completely normal.

It is natural, but it sounds somewhat formal and administrative.

A native speaker might expect this kind of sentence in:

• customs paperwork
• shipping forms
• postal declarations
• official descriptions of a parcel

In casual everyday speech, people might say something simpler depending on context, such as:

• Trong bưu kiện có hàng hóa. = There are goods in the package.
• Bưu kiện này chứa hàng hóa. = This package contains goods.

So your sentence is correct and natural, especially in an official context.

A native speaker would probably understand it as an official statement meaning something like:

• The contents of the international parcel are goods.
• This international package contains merchandise.

It sounds like the sentence is identifying the type of contents for mailing or customs purposes, rather than describing the package in a casual conversation.