I am wanting to breastfeed and pump with this baby he is not my first child but my first on wanting to breastfeed and pump. My question is how do i know what flange size I need? I have the motif Luna breast pump. I’m not sure how to work it or what settings I need it on. I really feel dumb but I’ve never breastfeed or pumped before. The flange size I have is 21mm,24mm,28mm. Any information for breastfeeding and breast pumping for beginners would be helpful