I just bought Pico-8 but where is splore.png?

To my knowledge, PICO-8 doesn't come with a SPLORE cart. On desktop, you just run SPLORE and it runs. If you got PICO-8 to run on a handheld, you have to create an empty file named "splore.p8" or "splore.p8.png" (make sure you don't accidentally have a .txt extension at the end or it won't work) and move that to wherever you put carts on the OS you're running on your handheld.