Set it from two things: how fast the item sells and how long the supplier takes. If you use ten kilos of chicken a day and your supplier delivers in two days, a par level of twenty is the bare minimum and thirty is safer.
Par levels are what stop the two expensive failure modes — running out of a bestseller mid-service, and tying up cash in a storeroom full of stock you will not use before it expires.
Review them seasonally. Ramadan, summer, and school terms move demand enough in Qatar that a level set in November will be wrong by May.
Outale lets you set a low-stock threshold per item and alerts you when stock falls below it, and products can carry a preferred supplier so reordering does not mean hunting for the contact.