Didn't we have to pack our bags? The trip was the following/next day.

[Sammy Sam]

When we talk about the coming day in Past

Which of the following statements are natural and grammatical?

1. Didn't we have to pack our bags? The trip was the following day.
2. Didn't we have to pack our bags? The trip was the next day.

Or should I add the preposition "on" in-between, like

3. Didn't we have to pack our bags? The trip was on the following day.
4. Didn't we have to pack our bags? The trip was on the next day.

I would really appreciate if my post is responded by the native speakers of English.

 

[emsr2d2]

When we talk about the coming day in the past, which of the following statements sentences are natural and grammatical?

1. Didn't we have to pack our bags? The trip was the following day.
2. Didn't we have to pack our bags? The trip was the next day.

Or Should I add the preposition "on" in-between, like as in the following sentences?

3. Didn't we have to pack our bags? The trip was on the following day.
4. Didn't we have to pack our bags? The trip was on the next day.

I would really appreciate if my post is responded by the native speakers of English.

Please note that I have improved your thread title. Titles should include some/all of the words/phrases/sentences you're asking us to look at. I moved your original title to the start of the thread and made it the start of a longer sentence. Note my other corrections.
Note that I have removed your final sentence. Please don't make requests like this. We have several very competent members whose native language is not English - it's unfair to try to exclude them from helping.

The use of "following" and "next" are both possible in 1 and 2. The use of "on" is wrong in 3 and 4.

I don't find "Didn't we have to pack our bags?" very natural because I can't think of a context in which it would be appropriate.

 

[Tarheel]

Assuming you have already gone on the trip, "Shouldn't we have packed our bags?" would work (if you didn't do that).