pay per episode

Often there will be options for whole seasons as well. In some (all?) markets, you would get discounted for any loose episodes that you may have bought already, when buying the season. The cost for the season would normally be less than the price per episode multiplied by the number of episodes in that season.

To get to the buy options different from the default, scroll down to How to Watch from the show’s details page, and see the listed options there.

Buy movies and TV shows from the Apple TV app - Apple Support

* You can buy entire seasons of a TV show or buy a Season Pass to get new episodes when they become available. A Season Pass for a TV show ends when all of the episodes in that season are uploaded by the provider. If you purchase one or more episodes of a show and then buy the entire season, the price of the entire season decreases by the amount that you already spent.

What service have you been streaming it from? According to Just Watch, the only streaming service that carries it is Max. It's available to purchase from Apple, Amazon and Fandango.

Okay, I double-checked. It doesn't appear to be available on Max anymore. That means you would need to purchase any episodes you want to watch.