'90s is a contraction of 1990s, or whatever other century's tenth decade is implied. So the apostrophe belongs as an example of a contraction or possessive :)

But your apostrophe is upside down (it became a curved single-open-quote in your version). It’s supposed to be this way:

’90s

Just 90s if it's a reference to someone's age. And the apostrophe for referencing the 90s era is optional outside of formal writing and a dash can also be used e.g.; 90s-music depending on context.