kaigi de ha, zyunban ni iken wo itte kudasai.

で marks the place or setting where something happens, so 会議で means in/at the meeting.

Adding は after that gives 会議では, which makes the whole phrase the topic or frame: as for in the meeting or when it comes to the meeting. It can also add a slight contrastive nuance, depending on context.

So:

• 会議で、順番に意見を言ってください。 = neutral At the meeting, please give your opinions in order.
• 会議では、順番に意見を言ってください。 = In the meeting, please do it this way / possibly contrasting with other situations

Both are natural.

It is pronounced de wa, not de ha.

That is because は is a particle here, and the particle は is pronounced wa.

So 会議では sounds like kaigi dewa.

順番 means order, sequence, or turn.

So 順番に means:

• in order
• one by one
• in turn

In this sentence, it suggests that each person should give an opinion one after another, following the decided order.

Here, に turns 順番 into an adverb-like expression.

So:

• 順番 = order / turn
• 順番に = in order / in turn

This に is not marking a destination here. It is making the noun describe how the action is done.

A similar pattern appears in words like:

• 静かに話す = speak quietly
• 別々に行く = go separately

Because 意見 is the thing being said.

The pattern is:

• 意見を言う = to state an opinion

So を marks the direct object of 言う.

Other similar examples:

• 名前を言う = say your name
• 本当のことを言う = tell the truth

Using が here would not be natural.

言って is the て-form of 言う.

Then:

• て-form + ください = please do ...

So:

• 言う = to say
• 言ってください = please say / please state

This is a standard polite request or instruction. It is polite, but still fairly direct, so it works well in meetings, classrooms, and announcements.

Japanese often leaves out the subject when it is obvious from context.

In this sentence, the listener is clearly the person or group being told what to do, so there is no need to say you.

In English, you usually need you, but in Japanese it is often omitted if everyone already knows who is meant.

Yes, to some extent.

Because Japanese uses particles like で, に, and を, the roles of the words are clear even if the order changes a little.

For example, this is also natural:

• 会議では、意見を順番に言ってください。

The original:

• 会議では、順番に意見を言ってください。

puts 順番に earlier, which highlights the idea of taking turns a bit more.

So the word order is somewhat flexible, but not completely free.

言う and 話す are related, but they are not the same.

• 言う = to say, to state
• 話す = to speak, to talk

In this sentence, each person is being asked to state an opinion, so 言う fits very well.

If you used 話す, it would sound more like talk about something or speak, rather than give your opinion as a specific statement.

So 意見を言う is a very common and natural expression.

会議 usually sounds fairly formal. It often refers to a business meeting, official meeting, committee meeting, or conference-style discussion.

It is less casual than something like a friendly get-together.

So in this sentence, the setting sounds organized and somewhat formal, which matches the instruction please give your opinions in order.