Swee-en-tee Mee-koh-lahj
* Swee-en-tee: The "w" is silent, and the "e" at the end of "Swiety" is pronounced like the "e" in "the."
* Mee-koh-lahj: The "j" at the end is pronounced like the "j" in "judge."
You can also hear the pronunciation by searching for "Swiety Mikolaj pronunciation" on a website like Forvo.