I need to know if I have friends.
...Also to evolve riolu...
The Friendship Checker is a person called Belamy who stands near the pastures in the east of Jubilife Village.
In order to get your Pokémon's friendship checked, you will first need to complete Request 28, 'Measuring Your Compatibility.' In it, Belamy wants to see a Pokémon that you've befriended. When you show it to him, he will be pleased and offer to check your Friendship levels in the future. He will also give you a Rare Candy.
In order to unlock the request, simply talk to him in Jubilife Village near the pastures.
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Hope I could help!