The Japanese language is not so strict about pluralization as English is.
Normally the word ねこ which means cat , can be a cat, some cats or cats in general. There are some specific words and suffixes to pluralize nouns, but when you are a beginner please don’t worry too much about whether they are singular or plural.
ねこが好きです。 I like cats ( in general )
あそこにねこがいます。can be “there is a cat over there” or “there are some cats over there”.
友だちと学校へ行きます。 can be ” I go to school with my friend ” or ” I go to school with my friends.”