Gamma2 Vittles Vault Pet Food Storage Containers - Sealed Dog and Cat Food Storage Container, Fits up to 25lbs, Made in the USA - [12"L x 13.75"H]

Buy grain by the sack and mill it yourself. If you need to store it, buy Gamma lid containers like these: https://a.co/d/059nPs06 I have three and have stored grain for a long time in them.

If at all possible put all human food in pantry closet or drawers. And lock drawers the same as cabinets with the lock like other comment. My cat opens drawers. Even my dresser drawers that are full. And she's a tiny grown cat. A comment mentioned that good boss with twist closures. I'll show an example link. https://a.co/d/0axlDWZa I've had mine for 11 years. Very worth the money. Also an idea that I will get with next kitten. https://a.co/d/0gEefcJG This is an example. Many different price points. But beware that the less price the louder during use. I hope these suggestions helped. Good luck.