Hi Hernandez I would say "Do you have the 20 pound Pedigree bag?" putting size before brand. Also, note how I used the positive form of the question..."Do you have?" This is super subtle, but it sounds slightly more natural and polite (in my opinion). The negative form might sound, to some people, a little challenging. Hope this helps!

To answer your first question about "the 20-pound Pedigree bag" vs "the Pedigree 20-pound bag", you could use either. In both forms my intonation would rise on the part that differs from what I was presented ("20-pound"). In your examples I would just add "bag" or "bag of" to them with "in a" being optional: Do/Don't you have the Pedigree (in a) 20-pound bag? Do/Don't you have the 20-pound bag of Pedigree?

I would agree with the points made by both Shawn and Paul, and say that "Do you have the 20-pound Pedigree (bag/one)," or "Do you have the 20-pound (bag/one) of Pedigree?" are the most natural answers. Here are some interesting resources explaining the order of adjectives in English: https://dictionary.cambridge.org/grammar/british-grammar/adjectives-order https://www.theguardian.com/commentisfree/2016/sep/13/sentence-order-adjectives-rule-elements-of-eloquence-dictionary I hope this helps!