It is not obligatory to offer expiation for watching movies, rather it is obligatory only to repent sincerely
Question

                My curiosity leads me to ask about some things so that I do not follow the wrong way which Allaah has forbidden… Previously we heard a fatwa from a shaykh whose name I do not know, that it is obligatory to offer expiation for watching dubbed [i.e. foreign] movies… Allaah knows best whether it was fasting forty days… On what is this expiation based, i.e., for what sin is it to be offered?… How should the Muslim offer expiation for these serials if he watched a number of them?… Does he offer one kafaarah for each episode or for each series, in which case he would have to offer 5 or 10 expiations…?
Praise be to Allah.
    What you have to do is to repent sincerely to Allaah, by 
    regretting this sin, giving it up and resolving not to return to it. You 
    should also pray a lot for forgiveness, and do a lot of righteous deeds, 
    because Allaah says (interpretation of the meaning): 

    “Verily, the good deeds remove the evil deeds (i.e. small 
    sins)”

    [Hood 11:114]
This is what will expiate 
    for your sin of looking at and listening to haraam things. With regard to 
    those who say that you have to offer expiation – such as the example you 
    mentioned – for watching movies, he has to produce evidence for that, 
    because it is not permissible to impose something upon the people without 
    sound evidence. Whoever imposes something on people that was not enjoined by 
    Allaah has ordained something in the religion for which Allaah has not given 
    leave. It is not permissible to invent expiations for sins and to specify 
    their type and number without evidence from sharee’ah. 

    Fasting in general terms, without specifying a particular 
    number of days, comes under the heading of good deeds which wipe out evil 
    actions. May Allaah help us and you to repent sincerely..