Fair enough, but since 'To' functions as a definite article (in this case 'the') vis-a-vis the English translation, it should still be there if the only correct English translation is "...the theatre."
What SteveKashkett means is: Either there should be a demonstrative pronoun before 'divadlo' or "We are seeking girls for theatre" should be an accepted translation.
"seek" is used without a preposition, unlike "look for" or "search for".
You cannot place "girls" at the end of the sentence -- unless what you want to say is that we are looking for "the theater girls," meaning some girls who are related to the theater as, for example, they work there. For that I would expect a different Czech sentence... but I am just learning Czech.