How does maternity leave work?

Sorry this is my first baby and i live in the US, Illinois Chicago ☺ I only work a part time job and I heard part timers don't get that benefit of paid maternity leave. Which is okay if that's the case I just want to know all the accurate info before I find out im missing out on something! Lol I work at a retail store, also how far along should I let them know that I can't work anymore? I'll be 7 months and still feel okay, how many weeks is it required to leave? Would I get fired for example if I don't come back in 4&6 week? I know I should ask my manager but my district manager is never at my location anymore and the assistant manager always gives false information and shes not a huge fan of my pregnancy (she has talked about me)so I don't want to go to her. Thanks!