Dear @Talha_Dar ,
So, the 'Defect Responsible' column is taken from the Sharepoint List with the data type "person" so that the name and email will appear automatically when searched in that column.
Well, previously I put the "Defect Responsible" column in the Form, but now what I want is the column outside the Form so I have to use a combo box.

I used this formula before, but it's still error
Sort(
Distinct(
'Monitoring RN',
'Defect Responsible'.Email,
'Defect Responsible'.DisplayName
),
'Defect Responsible'.DisplayName,
SortOrder.Ascending
)
What is the formula so I can use the combobox and retrieve the data from the Sharepoint List with the data type "person"? Thank you