There are different ways to get the plural of a noun. If you have words already ending in "-e" the plural will most definitely just get an "-n". Like "der Name" gets "die Namen" in plural. Some words even get "-en" to achieve the plural like "die Frau"/"die Frauen" or "der Herr"/"die Herren". Others ending in "-l" just get an "-n" like "die Fackel"/"die Fackeln". So the most plural words would end in "-n" I would say. But many also get just an "-e". Like "das Pferd"/"die Pferde". In some cases there is the ending "-er" added: "das Kind"/"die Kinder" or an additional vowel change to an umlaut "das Horn"/"die Hörner". Some don't change at all "der Eimer"/"die Eimer". That does not accure with feminine nouns though because you could not differentiate them from the singular form then. And quite a few words get the ending "-s" like in English. For example: "das Auto"/"die Autos", "das Handy"/"die Handys", "der Akku"/"die Akkus". They would mostly end in other vowels beside "-e" then. Some words with foreign heritage have irregular plurals like: "der Kaktus"/"die Kakteen", "der Globus"/"die Globen", "das Opus"/"die Opera". You will get to know these one by one and eventually it will come naturally to you.
I hope I could be of help.
Unfortunately it is not that simple. German has quite a few different patterns of forming plurals, and I'm afraid you will have to learn them. This is a good overview over plural formation:
Careful: All examples given show only the nominative case! Particularly masculine nouns may also have in plural changes in cases!
I think one might as well say plural nouns acquire an -n ending in the dative case, the gender doesn't matter; this is a feminine noun:
- Nominative: die Hände
- Genitive: der Hände
- Dative: den Händen
- Accusative: die Hände
So other than that plural nouns don't change in cases as far as I know.
The audio isn't fantastic here but it definitely isn't saying Pferd. One thing to look out for is the devoicing of final consonants, Pferd is actually pronounced Pfert, so the fact that a voiced d can clearly be heard along with a short vowel at the end should make it clear that it's the plural.