After you purchase the swim suits, where do find them at?

If you purchased the swim suit in the specialty store it probably won't go in the wardrobe section I say this because I built a home pool and my task to fulfill was for my Sim to relax in a pool chair. When I tapped the pool for her to get in she automatically changed into a swim suit, and I haven't built the specialty store yet. It happens like when they take a shower by spinning. Hope thus helps. Good luck.

Well you will only be able to see it when your sim goes Swimming, has a shower, or when you click on the wardrobe and choose change into swimsuit. But if you mean where can you see swimsuits you unlocked with an in-app purchase, those would probably be in the costume shop, where all the other swimsuits are for sale and you can change your sim's default swimsuit.