10 I've got a little/lots of/much pairs of jeans but these are my favourite.

Lots of is the correct answer.
Explanation: "Pairs of jeans" is a countable phrase, even though the word "jeans" is considered plural but uncountable in some contexts, because it's used with "pairs." "A little" is for uncountable nouns, and "much" is for uncountable nouns. "Lots of" means a large amount or number and is the appropriate choice.
Answer: lots of