3 We (just/visit) the Eiffel Tower. Now I think we (go) to the Louvre.

We visited the Eiffel Tower. Now I think we are going to the Louvre.

We visited the Eiffel Tower. The past simple tense 'visited' is used to describe a completed action in the past.
Now I think we are going to the Louvre. The present continuous tense 'are going' is used here because it expresses a planned action in the near future.