kodutumi no nakami wo kakuninsite kara, okurimasu.

Literally, 小包の中身 means the contents of the package.

• 小包 = parcel / package
• 中身 = contents / what is inside
• の links the two nouns

So A の B often means B of A or A’s B.
Here, 小包の中身 is the package’s contents, or more naturally in English, the contents of the package.

Both are related to inside, but they are not the same.

• 中（なか） = inside, interior, the inside part
• 中身（なかみ） = the contents, what is actually inside

So:

• 小包の中 = the inside of the package
• 小包の中身 = the contents of the package

In this sentence, the person is checking what is inside, so 中身 is the better word.

を marks the direct object of the verb.

Here, the verb is 確認して / 確認する = to check / confirm.
What is being checked? 小包の中身.

So:

• 小包の中身を確認する = to check the contents of the package

That is why を is used.

確認してから means after checking or check first, and then...

It is made from:

• 確認する = to check / confirm
• 確認して = the -て form
• ～てから = after doing ~

So:

• 確認してから、送ります。 = After checking, I will send it.

This pattern is very common when one action happens before another in a deliberate order.

This is a very common learner question because から has two different uses.

1. ～てから = after doing ~
2. ～たから = because ~ did

So:

• 確認してから、送ります。 = After checking, I will send it.
• 確認したから、送ります。 = Because I checked it, I will send it.

In your sentence, the meaning is about sequence of actions, not reason, so ～てから is correct.

Japanese sentences usually place the main verb at the end.

Here, the whole sentence builds up to the final action:

• 小包の中身を確認してから、 = after checking the package’s contents
• 送ります = I will send it

This end placement is normal in Japanese. English often puts important information earlier, but Japanese usually saves the main action for the end.

The subject is omitted, which is very normal in Japanese.

From context, it is usually understood as something like:

• I will send it
• we will send it
• sometimes someone will send it

In many Japanese sentences, if the subject is obvious from the situation, it is simply left out.

So the sentence does not explicitly say I or we, but in many contexts an English translation would naturally use I.

The thing being sent is understood from context, and most naturally it is the package.

The sentence says:

• Check the contents of the package
• then send it

Even though 小包 is not marked as the object of 送ります, Japanese often leaves repeated information unstated if it is already clear.

So the implied meaning is basically:

• I’ll check the contents of the package, and then send the package.

In Japanese, 送ります can cover both present/future depending on context.

Here, it is most naturally future:

• I will send it

Japanese does not usually separate present and future as clearly as English does. The non-past form 送ります can mean:

• send / sends
• will send

In this sentence, because it follows after checking, the future interpretation is the natural one.

The verbs are in polite form:

• 送ります instead of 送る

Also, 確認して comes from 確認します / 確認する, and in this structure the -て form is used.

This makes the sentence suitable for neutral polite conversation, customer service, workplace communication, emails, and so on.

A plain-form version would be:

• 小包の中身を確認してから、送る。

That sounds more casual.

The comma is mainly there to make the sentence easier to read.

• 確認してから、送ります。

It separates the preliminary action from the main action.
Japanese commas are often flexible, so this comma is helpful but not absolutely required.

You could also see:

• 小包の中身を確認してから送ります。

with no comma, and it would still be correct.

You could use other expressions, but they would not mean exactly the same thing.

For example:

• 小包の中身を確認したあとで、送ります。

This also means After checking the contents of the package, I will send it.

Compared with ～てから:

• ～てから is very common, simple, and natural
• ～たあとで sounds slightly more explicit about the action being completed first

Both are correct here.
Still, 確認してから、送ります。 is a very natural everyday phrasing.