Fódlan is the latest continent introduced to the Fire Emblem universe and is the setting to Three Houses. Like Magvel, it is another world that does not have another game taking place within it.
Do you need to play the other Fire Emblem games before Three Houses?
No need to play any previous entry’s for the sake of the story. If you’ve never played a fire emblem game before you might want to try a game like sacred stones ( FE 8 ) to familiarize yourself with the basic mechanics in fire emblem so it won’t all be new to you.