How to change format of "Date format" field to Dropdown in user's profile page in Service Portal

[date]

We have to add Date format field in the user’s profile page on the portal and it should be in the same format as the “Time zone"  and Language field. Attaching the screenshot for your reference.

Currently, The field behavior is that it is opening up a dialog window to choose the date format but we want to behave similar to time zone and language field means as a dropdown.