Verified Answer :

You're welcome is the correct spelling since it is the contraction of "You are." Your is a possessive pronoun, indicating ownership. For example, saying "your welcome" means that you own "welcome," which doesn't make much sense. Hope I helped :)

Answer:

you're welcome

Explanation:

if you don't want to use a contraction then you can also write you are welcome... but we don't see anyone saying really anymore right?