Hi @Ana_Montaño_Medina_S, welcome to the Asana Community Forum!
If you are importing tasks to Asana using a CSV file, the supported format is MM-DD-YYYY. When your tasks are imported, you will see the tasks due date in the format that you have in your browser, in your case DD-MM-YYYY.
If you still don’t see the correct format after importing your tasks, please ensure that there is no VPN active in your device and contact our support team so we can investigate further: How to contact our Support Team ✉
Hope this helps!