Here's the answer:
“¿estos son mis calzoncillos?”
Watch a real native speaker say it:
Here's how it sounds in a textbook:
You could also say:
- ¿son estos mis calzoncillos?
- ¿son mis calzoncillos?
Fun fact: the hundreds of thousands of people learning Spanish with Memrise get this phrase correct 95.12% of the time!