Is Porto der, die or das?

The correct German article for Porto is das. The noun Porto is Neuter. So you always say: das Porto. Learn the article together with the noun — German nouns don't follow predictable gender rules most of the time.

The plural of Porto is: die Portos. In the plural, every German noun takes the article "die". So: die Portos. Example: ein Porto → zwei Portos.

Correct: die Portos. The form "die Portos" is wrong. The plural of das Porto is die Portos. In the nominative plural, you always use the article "die".

das Porto follows the four German cases. Nominative: das Porto, Accusative: das Porto, Dative: dem Porto, Genitive: des Portos. In plural: die Portos / den Portos. Learn these forms together with the noun.

The genitive singular of das Porto is: des Portos. The genitive plural is der Portos. German uses the genitive to express possession or belonging. Example: die Farbe des Portos.

The dative plural of Porto is: den Portos. In German, dative plural nouns usually end in "-n". So you say: "mit den Portos". Use this case after prepositions like mit, von, bei, zu.

Porto is a noun and must be capitalized in German. You'll find example sentences above for each case. The article das stays the same in nominative singular but changes in other cases. Practice declension in your own sentences.

Yes, Porto is a noun (also called a substantive). German nouns are always capitalized. The article for Porto is das. Every German noun has a fixed article you must memorize.