How can i ask my ex gf if she wants to be Friends With Benefits? (FWB)'s?

my gf and i broke up about 3 weeks ago, we are okay with beiing friends, she only broke up with me because she wanted to be single, and didnt want to be in a seious relationship, ad i didnt do anything wrong. she liked when we made out and did ual things. she tells me that we can chill or hang out 1 day at the movies, how should i ask her for ?