Please help me first time mom - to all rhe breastfeeding and pumping mothers - how do I pump and freeze or save it v

So I’m ebf. My baby is 6 months old. She won’t take a bottle and it is really hard to ever get a break when I’m the only one that can feed her. I bought a motif pump and it will be here in a few days. Also a dr browns bottle because she liked them when she was a week old then decided she didn’t want a bottle anymore. So my question is

I’m going to start pumping for random times when I need it or if I need to go somewhere for a few hours , I’m going to buy those bags you can store milk in , any recommendations? Also I’m super confused about it. I put it in the bag And then I can just freeze it ? How long does it last ? How to I thaw it and warm it ? Can it not go in the fridge ?