mullon, ubido baenange isseo.

물론 means of course, naturally, or certainly. At the beginning of the sentence, it sets the tone: the speaker is saying this as something expected or obvious.

So 물론, 우비도 배낭에 있어. has the feeling of:

Of course, the raincoat is in the backpack too.

우비 means raincoat, rain gear, or sometimes rain poncho, depending on the situation.

It is a practical word for clothing worn to keep off rain, especially outdoors. In hiking or travel contexts, 우비 can sound more like rain gear than a stylish coat.

도 means also, too, or sometimes even.

So 우비도 means the raincoat too or also the raincoat.

This tells you that the raincoat is not the only thing being talked about. Something else was probably already mentioned as being in the backpack.

For example, the implied context could be:

• 물도 있어. 우비도 배낭에 있어.
• There’s water too. The raincoat is also in the backpack.

With 있다, Korean uses 에 to mark the place where something exists or is located.

• 배낭에 있어 = is in the backpack

By contrast, 에서 is usually used for the place where an action happens:

• 학교에서 공부해 = study at school

Since 있다 here is about location/existence, 에 is the correct particle.

있어 is the present-tense casual form of 있다.

Here, 있다 means to be / to exist / to be located, so 배낭에 있어 means is in the backpack.

Speech-level comparison:

• 있다 — dictionary form
• 있어 — casual speech
• 있어요 — polite everyday speech
• 있습니다 — formal speech

So this sentence is in a casual style. If you wanted to say it politely, you would say:

물론, 우비도 배낭에 있어요.

It is omitted because Korean often leaves out subjects and topics when they are already clear from context.

English usually needs something like it, there, or a repeated noun, but Korean often does not.

So the full idea might be something like:

• (그건) 물론, 우비도 배낭에 있어.
• Of course, the raincoat is in the backpack too.

The listener is expected to understand the missing part from the conversation.

Yes, to some extent. Korean word order is flexible because particles show each word’s role.

For example, these are both natural:

• 우비도 배낭에 있어.
• 배낭에 우비도 있어.

The difference is mostly about emphasis:

• 우비도 배낭에 있어 slightly highlights the raincoat too
• 배낭에 우비도 있어 slightly highlights in the backpack

Both mean essentially the same thing.

No, it is not strictly necessary.

The comma just shows a small pause after 물론. In writing, this can make the sentence feel a little clearer or more natural. In casual writing, many people would simply write:

물론 우비도 배낭에 있어.

So the comma is a style choice, not a grammar requirement.