@Amandine Legal - This is not currently possible using out-of-the-box Miro functionality.
it may be possible using using the Miro Developer Platform to build a custom application using the REST API, however, that is a pretty involved workaround. You would probably want someone with a development background to review the developer platform documentation.
Reach for the stars…
You could request this functionality in the form of an Idea in the Wish List category by following the guidelines here: Wish List: Everything You Need to Know.
If you do create a Wish List Idea post, I would also recommend that you post a link to it back here, so that future readers of this post can quickly get to and vote for your Idea.
Lastly, don't forget to vote for your own Idea.