How to use a salesforce flow builder to display the value of who.name in a record field "Name" on event object?

Hi, I'm looking to display the Who.Name in a report field "Nom" and I created a formula field "Nom" with the formula : Who.Name.

It didn't work then I used the Who.Id formula instead and  it displayed the Id of the contact link to the event as showned in the screeenshot attached.

I  found out it is possible to transform these WhoIds into Who.name through Flows but i'm quite limited on flow.  Is there anyone who knows how to do it step by step ?

Thanks a lot