Unfortunately, there are so many mistakes in the sentences, it is not just about the two words you are asking for.
*In case of fire, do not use the lift.* (=if a fire happens)
*You didn't do your homework? In that case, you can't watch TV.* (=since you didn't do your homework)
"In the case" is used rarely, and refers to KNOWN options. E.g. it might rain or it might not rain. In the case that it rains, we stay indoors. In the case that it doesn't rain, we go outdoors.
PS. You might want to work a lot harder at your grammar.