Paku la produkton en la malnovan skatolon.

Paku is the -u verb form, which is used for commands, requests, instructions, and similar ideas.

• paki = to pack
• paku = pack!

So Paku la produkton... means something like Pack the product...

In Esperanto, the -u ending does the job that English often does with the bare verb:

• Manĝu! = Eat!
• Venu! = Come!
• Paku! = Pack!

The subject is usually understood as you.

The -n marks the direct object.

Here, la produkton is the thing being packed, so it gets -n:

• la produkto = the product
• la produkton = the product as the direct object

This is a very common feature of Esperanto. The direct object usually takes -n no matter where it appears in the sentence.

Compare:

• Mi vidas la produkton. = I see the product.
• Paku la produkton. = Pack the product.

In both cases, la produkton is the direct object.

They have -n because en la malnovan skatolon shows motion into the box.

In Esperanto, a prepositional phrase can also take -n when it indicates direction toward a place, not just location.

So:

• en la malnova skatolo = in the old box (location)
• en la malnovan skatolon = into the old box (direction/movement)

Since the sentence is about putting or packing something into the box, the directional -n is used.

Also, the adjective has to match the noun, so both change:

• malnova skatolo
• malnovan skatolon

This is a very important distinction:

• en la malnova skatolo = in the old box
  This describes a location.

• en la malnovan skatolon = into the old box
  This describes movement toward the inside of the box.

In this sentence, the idea is not just where the product is, but where it is being placed. That is why Esperanto uses the directional -n.

A helpful way to remember it:

• no -n = where?
• -n = to where?

In Esperanto, adjectives agree with the nouns they describe in both:

• number
• case

So if the noun is plural, the adjective becomes plural too.
If the noun has -n, the adjective gets -n too.

Here:

• skatolo = singular noun
• skatolon = singular noun with -n
• malnova = adjective
• malnovan = matching adjective with -n

So la malnovan skatolon is correct because both words must match.

Examples:

• la granda domo = the big house
• la grandan domon = the big house as object / with direction
• la grandaj domoj = the big houses
• la grandajn domojn = the big houses as object / with direction

Yes. mal- is a very common Esperanto prefix meaning the opposite of.

So:

• nova = new
• malnova = old

That means malnovan is just malnova with -n added to match the grammar of the phrase.

This prefix is used a lot in Esperanto:

• bona = good
• malbona = bad
• varma = warm
• malvarma = cold
• dekstra = right
• maldekstra = left

Esperanto uses la as the definite article, meaning the.

So:

• la produkton = the product
• la malnovan skatolon = the old box

There is only one definite article in Esperanto: la. It does not change for gender, number, or case.

Also, Esperanto normally has no indefinite article. So:

• produkto can mean a product or product
• la produkto means the product

Using la twice here is perfectly normal because both noun phrases are definite.

Yes. In a command with -u, the subject is usually understood to be you.

So:

• Paku la produkton... = Pack the product...
• more explicitly: Vi paku la produkton... = You should pack the product...

In ordinary commands, Esperanto often leaves out vi, just like English usually leaves out you in commands.

Yes, Esperanto word order is fairly flexible because endings show grammatical roles.

The most neutral order here is:

• Paku la produkton en la malnovan skatolon.

But other orders are possible, especially for emphasis:

• En la malnovan skatolon paku la produkton.
• La produkton paku en la malnovan skatolon.

Even when the order changes, produkton is still the direct object because of -n, and en la malnovan skatolon still shows direction into the box.

That said, the original order is the most straightforward for learners.

Usually en is the natural choice when something goes into something.

• en = in / into

Because the product is being packed so that it ends up inside the box, en works well.

Esperanto often expresses into as:

• en
  • -n

So:

• en la skatolo = in the box
• en la skatolon = into the box

That is one of the standard ways Esperanto handles movement into a place.

No. The -u form can sound like a command, but it can also be:

• an instruction
• a request
• a suggestion
• a direction in a manual or recipe

So Paku la produkton en la malnovan skatolon could mean:

• a direct order
• a polite instruction, depending on context
• a step in a process

Tone in Esperanto, just like in English, often depends on context, voice, and situation rather than grammar alone.