What event is the most convenient one for the Estimation

The Scrum Guide makes it clear that estimation is a part of Product Backlog refinement:

Product Backlog refinement is the act of adding detail, estimates, and order to items in the Product Backlog.

It's important to note that Scrum does not specify how Product Backlog refinement gets done. There is no prescribed meeting or event associated with refinement, although in my experiences, teams do find a meeting useful to synchronize on refinement activities. Frameworks to scale Scrum, such as Nexus and LeSS, do elevate refinement to an event.

It's also important to realize that one of the outcomes of the Sprint Review may be changes to the Product Backlog. The backlog could reflect these changes with the addition, removal, or reordering of items. If items are added or reordered, a Product Backlog item that was not well refined may now be closer to the top of the backlog. In these cases, the team usually performs refinement at the Sprint Planning to determine if there's enough information to understand the work, assess its size, and see if it is appropriate for the Sprint.

Ultimately, I'd recommend working with the team to understand how to perform refinement and planning can best. It may be necessary to experiment with a few different methods to find what works best in your context.

I am a new Scrum Master for a newly formed team, so I want everything to be ideal :) at least similar to the ideal Scrum,

So, I am organizing all the events, including Backlog Refinement session,

I'm going to start here.  Scrum is a framework so in my opinion there is no such thing as "ideal Scrum".  Scrum is adapted to be functional for each team that is using the framework.  It is not totally prescriptive and provides some guidance on events, roles and artifacts that are designed to help with inspection and adaption as you work.

"Backlog Refinement session" is not one of those events or artifacts. In fact refinement of the Product Backlog is only mentioned in the Scrum Guides section that describes the Product Backlog(https://scrumguides.org/scrum-guide.html#artifacts-productbacklog). The sixth paragraph and one sentence in the seventh paragraph are the only mentions of refinement in the entire guide.  It is an ongoing activity that is done in the best way for the team. I have worked with teams that never got into a room together for the purpose of refinement.  They did it via comments in the tool we used for tracking Product Backlog Items  (PBIs) or chat conversations in our internal messaging appliication. 

So, I just wonder at what event should the estimation in story points done? 

As with refinement, estimation is not clearly defined in the Scrum Guide either.  The majority of the discussion is also contained in the section that describes the Product Backlog.  Estimates are loosely tied to the activity of refinement because the better you understand a problem the better you can estimate the effort needed.  Since there is no event for refinement, my opinion is that there is not a best place for it to occur because it will naturally happen as the problems are better understood. 

One more thing to call out.  User Stories and Story Points are not mentioned at all in the Scrum Guide.  They are a practice that has been adopted and changed by the agile world from eXtreme Programming (XP).  In XP, estimates were placed on User Stories when the team discussed the item and the points evolved as more information was known about the User Story.  An estimate should be made based on all information you have at the time that the estimate is done. Estimates are useful for for a team to become comfortable enough to start work but beyond that their usefulness is subjective.  And this is my opinion but once work starts you should stop focussing on the estimate and focus entirely on completing the work as soon as possible without sacrificing the quality or value of the deliverables. 

The sequence is the following: 1. Stand Ups, 2. Backlog refinements, 3. Sprint planning, 4. Sprint review 5. Retrospective

Are you sure that Product Backlog refinement belongs in a sequence at all, when the work is emergent?