First thing is I would say your thinking is a bit rigid. In a brief emergency situation eating 3 square, nutritious meals a day isn't a priority. The thing you want to make sure of is that you're not uncomfortably hungry or thirsty. You don't need to plan for meals.
If you look in your kitchen cupboard, do you currently have 3 days worth of food in there? What shelf stable food do you normally eat? Buy an extra one or two of each item and keep it in your cupboard if you've room, or a box somewhere else is you haven't the cupboard space. Buy stuff you like, and from that point on, always keep the surplus of food constant as you eat it.
If you buy stuff you don't normally eat and have it in a separate kit, you won't end up eating it, it'll go out of date and you'll throw it away.
For us we have:
Drinks
Bottled water, uht milk, fresh milk in the fridge and I freezer, alcohol free beer
Carbs/fats/sugars
Cereal, porridge, nuts, jam, honey, bread in the freezer, cereal bars, biscuits, crackers, chocolate, crisps, butter, oil, sugar, flour, christmas cake
Protein
Tinned tuna, tinned salmon, tinned mackerel, corned beef, cheddar in the fridge, eggs
Fruit/veg
dried fruit, tinned sweetcorn, mushy peas, tinned pineapple, baked beans, mixed beans, tinned green lentils, tinned chickpeas, frozen peas, frozen mixed veg, frozen sweetcorn, frozen berries, fruit and veg in the fridge
Non of that needs cooking. We wouldn't be hungry, but we wouldn't be eating normal meals. It would be fine for a few days to a few weeks.
The only thing on that list that I don't normally keep in the house is bottled water and uht milk.