Hi @Antoine_Ibanez ,
Before writing it into the excel Please convert it into the text as required format as shown in below image.

Another method is after writing it to the excel.Please run VBscript using RunVbscript action.
VBCode:
Option Explicit
Dim xlApp, xlBook, xlSheet
Dim lastRow, i
' Create an instance of Excel
Set xlApp = CreateObject("Excel.Application")
' Open the Excel file
Set xlBook = xlApp.Workbooks.Open("C:\path\to\your\file.xlsx")
' Set the active sheet (change the sheet name if necessary)
Set xlSheet = xlBook.Sheets("Sheet1")
' Find the last row with data in column C
lastRow = xlSheet.Cells(xlSheet.Rows.Count, "C").End(-4162).Row
' Loop through each cell in column C and change the date format
For i = 1 To lastRow
If IsDate(xlSheet.Cells(i, "C").Value) Then
xlSheet.Cells(i, "C").NumberFormat = "dd/MM/yyyy"
End If
Next
' Save and close the Excel file
xlBook.Save
xlBook.Close
' Quit Excel application
xlApp.Quit
' Release the objects
Set xlSheet = Nothing
Set xlBook = Nothing
Set xlApp = Nothing
' End of script
(Note:- if you got your solution you can mark as solution and gives kudos)
Thanks & Regards
Vishnu Reddy