There are some ways to reply to "thank you" in Korean,
but "천만에요(cheon-man-e-yo )" is mostly used to mean "you're welcome" in a textbook.^^
Here is a variation of it.
(You can pick one of them up because it's a matter of preference, and all are polite)
^.^ (just smiling without saying anything like me ^^)
"별말씀을요(byeol-mal-sseum-eur-yo)"
"뭘요(meor-yo)"
"괜찮아요(gwaen-chanh-a-yo)"
^_____^