In the cities, we used to buy food for rubles in grocery stores, most of which were called Produkty or Gastronom. We had them everywhere, all owned by the government.
There was no room for private shop owners, and shops had no branding. That made it real simple to find food in the Soviet. You had to go down a couple of blocks looking for big friendly letters saying “Producty” (groceries), or “Gastronom” (food), or if you are in a bigger city “Kolbasa” (processed meat), or “Ryba”/”Okean” (“fish”/”seafood”).
No guarantee that you would find anything beyond the basic butter, milk or birch sap (a staple item, always in 3-liter glass containers). But if you saw a line forming inside or outside, it was a good sign: they had a fresh delivery of some rarer stuff.
In the picture below, a Gastronom shop, the way they looked like when I was little. I learned to read when I walked down the street with my parents and matched letters in shop signs to the sounds that grown-ups made of them.