DropdownList value in View

Hi, I have recently used Yii2 and I have a question about Dropdownlists: I load a Dropdownlist from a Nations table of a DB (id_nation, nation), I see the list of countries, I select Spain, Salvo and in the View I see the id_nation.
How do I see the nation value?
Are there already posts with this solution?

Thank you

Do you have a relationship between your tables?

Yes :: (Nations) id_nazione --> p_nazione (STATES_REGIONS) and it’s called ‘stati_regioni_ibfk_1’