Help How does Nihongo differentiate between singular and plural for a noun?

In English we add an "s" usually. E.g. "car" is "cars", "pen" is "pens", etc.

If I wanted to differentiate a noun in this way, e.g. "newspaper" and "newspapers", what is the method used in Nihongo?

For example in Korean you add "deul" to the end. Person=saram People=saram-deul

In almost all cases, there is no distinction.

In a few cases, a suffix can be added or the word may be repeated (doubled). Sometimes number may be mentioned, or things equating to "few", "several", "only" may already.

Although it can be hard to get used to if you grew up speaking a language that routinely distinguishes between singular and plural, you eventually come to realize that the lack of the distinction is a total non-issue in Japanese.

I think deul (들) in Korean has its root in the Chinese 達. In Japanese, this character is pronounced "tachi", and is used as a suffix to denote the plural of (usually) animate objects. In other words, I think -tachi is a cognate of deul.
Kodomo - child, kid
Kodomotachi - children, kids
(Although, as Mike says above, even without the -tachi, the word kodomo by itself can indicate several children, which, I think is the same case in Korean also?)
Normally -tachi is only used for animate objects. If you use -tachi to indicate plural of inanimate objects, you will be understood, but it is a bit idiosyncratic.