ie ni kaette kara, rezibukuro no naka no pan no syoumikigen wo kakuninsita.

A natural way to parse it is:

• 家に帰ってから = after going home / after getting home
• レジ袋の中のパンの賞味期限を = the best-before date of the bread in the shopping bag
• 確認した = checked / confirmed

So the overall structure is:

After getting home, [I] checked the best-before date of the bread in the shopping bag.

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

Here, から is part of the grammar pattern verb in て-form + から, which means after doing something.

So:

• 帰ってから = after returning home

This is different from から meaning because.

Compare:

• 家に帰ってから、確認した。 = After I got home, I checked.
• 家に帰ったから、確認した。 = Because I got home, I checked.

So in this sentence, it is definitely the after meaning.

With 帰る (to return/go back), the destination is often marked by に or へ.

So:

• 家に帰る
• 家へ帰る

Both are correct. に is very common and often feels a little more neutral/direct.

You would not normally say 家を帰る here, because を does not mark the destination with 帰る.

Because 〜てから is a fixed grammar pattern.

• 帰ってから = after returning
• 帰ったから = because I returned

Even though the action happened in the past, the form before から is still the て-form in this pattern.

If you want another way to say it, you could use:

• 家に帰ったあとで

That also means after I got home.

レジ袋 means a plastic shopping bag or checkout bag from a store.

It is made of:

• レジ = cash register / checkout
• 袋 = bag

So it literally means something like checkout bag.

In modern Japanese, this usually suggests the thin plastic bag you get at a store.

This is easiest to understand from right to left.

1. 賞味期限 = best-before date
2. パンの賞味期限 = the bread’s best-before date
3. 中のパン = the bread in/inside
4. レジ袋の中 = the inside of the shopping bag

Put together:

• レジ袋の中のパンの賞味期限 = the best-before date of the bread inside the shopping bag

Japanese often stacks nouns with の like this, where English would use phrases like in, of, or relative clauses.

レジ袋の中のパン is a shorter, more compact way to say:

• レジ袋の中にあるパン = the bread that is in the shopping bag

In Japanese, noun + の + noun can sometimes do the job of a longer descriptive phrase.

So:

• レジ袋の中のパン is natural and concise
• レジ袋の中にあるパン is also correct, but longer and more explicit

The shorter version is very common in everyday Japanese.

This is an important vocabulary distinction.

• 賞味期限 = best-before date
  It means the food is expected to keep its best quality until that date.
• 消費期限 = use-by date
  This is used for foods that spoil more easily and should be eaten by that date.

In English, both are sometimes loosely translated as expiration date, but in Japanese they are not the same.

So in this sentence, the speaker checked the 賞味期限, meaning the quality/recommended date, not necessarily a strict safety deadline.

Because 確認する takes a direct object: the thing you confirm/check.

So here:

• 賞味期限を確認した = checked the best-before date

The whole object is actually:

• レジ袋の中のパンの賞味期限を

So を marks that entire noun phrase as the thing being checked.

確認する means to check, to confirm, or to verify. It suggests a deliberate action.

• 見る = to look at / to see
• 確認する = to check/confirm carefully

So:

• 賞味期限を見た = I looked at the best-before date
• 賞味期限を確認した = I checked the best-before date

The second one sounds more natural if the purpose was to make sure what the date was.

Japanese often omits the subject when it is clear from context.

So this sentence does not explicitly say:

• I
• he
• she
• we

Any of these could be the subject depending on context.

If the sentence appears by itself in a textbook, it is often most natural to translate it as I checked..., but the Japanese itself does not force that interpretation.

Japanese nouns usually do not show singular vs. plural the way English does.

So パン can mean:

• bread
• a loaf of bread
• a bread item
• breads

Context decides.

In this sentence, it probably refers to a specific bread item or package in the bag, because there is one 賞味期限 being checked. But Japanese itself does not explicitly mark the number.

Here, 家 is best understood as home.

Even though 家 literally can mean house, in expressions like:

• 家に帰る

it usually means go home rather than go to the house in a purely physical sense.

So the nuance is about returning to one’s home/place of living.