I had sex march 20th 2018 but the condom broke, two hours later i took plan b. i was supposed to ovulate the next day. will the pill work ?

Plan B should work: Plan B works very well when taken the day of sex or the day after sex. However, very well is not perfect (and nothing in this world is perfect), so there is a small chance of pregnancy. Plan B can alter one's menstrual bleeding for 1-2 cycles, so a late period doesn't necessarily mean a pregnancy. One should do a home pregnancy test 3 weeks after sex, to see if there is a pregnancy.