Honestly 3 days is less than most people just already have. People laughed at me before Covid but I’m immunocompromised and get sick really easily so I always have a stockpile in.
I have a camping stove with 12 gas canisters. Batteries and torches and candles.
5x5l drinking water
12 tins of soup/beans &sausage/meatballs
6 of those dried pasta and sauce things
3 tins corned beef
3 tins hot dog
Large tub of dried mash
12 various tinned veg
1kg sealed porridge oats
12 tinned fruit cocktail/grapefruit/mandarins
1 jar coffee
1 pack teabags
hot chocolate
ambient squirty cream
dried milk
4 condensed milk
3 boxes of cupa soup
sweets/chocolate/biscuits
sugar
emergency first aid medical kit
extra concentrated cordial squeeze pots
I also have other stuff like cards, board games, head torches for reading in the dark, spare guitar strings, crochet hooks and yarn and those glow sticks that you can make jewellery from to keep the kids entertained in power cuts. Basically is all the same stuff I’d take camping and I use it and replace it so it’s always got a decent shelf life. I already buy toilet rolls and cleaning products in bulk so I’m pretty set tbh. I also live on the very top of a hill that’s often inaccessible during snow so it totally makes sense for me to have things in place.
and all of that ^ is on top of my normal cupboards, chest freezer and fridge. I also have a multi fuel bbq and a Dutch oven so can even bake my own bread as I always have 6kg+ of flour in the house plus tons of other baking ingredients. I would empty the freezer first in an emergency and use that. We could probably last 4-6 weeks easily before I got fed up and started running low.