Yes, nearly all nouns add an -en or -n in the dative plural if they don't already end in -n or in -s.
Also, masculine and neuter nouns often add an -(e)s in the genitive, e.g. des Vaters "of the father".
That's about it, though; there used to be a masculine/neuter dative ending -e but this is now just about obsolete except in fixed expressions such as zu Hause.
Different nouns form their plural in different ways.
Most feminine nouns in -e have a plural in -en, e.g. die Ente - die Enten
But die Kuh dies not end in -e. The plural of that noun happens to be die Kühe.
Plurals can be in -e, -en, -er, -s, or with no ending; and with or without umlaut.
In general, you have to learn the plural together with the word, since it's not generally predictable.
-.- i really dont like the man when he speaks, i feel he slurs his words or rushes and its not very clear. ( for me at least ) I have to make him "slow down" so i can understand it and translate properly... I got this one wrong like 4 times trying to do it without the slowing.