what is the equivalent part of "the" in turkish ?

Bir çeviriye bakın

There's no equivalent of "the" for subjects in Turkish. The definite article "the" can only be used with objects in sentences.
For example:
"Film güzeldir." Since film is the subject of this sentence, there's no way to distinguish if it is a specific movie or not. This sentence can mean both "Movies are nice." or "The movie is nice."

But if the word is the object of the sentence, there is a way to make it specific: the accusative suffix -ı/-i/-u/-ü:
Film izledim = I watched a movie.
Filmi izledim = I watched the movie.