I'm looking for a quart of milk.
I want to buy a half pound of butter.
I have a bag of flour.
I eat sandwich with a jar of jam.= I eat a sandwich with a jar of jam.
I like a pint of ice cream.

Great work overall! You correctly used quantity phrases (like a quart of milk, a bag of flour) with non-count nouns. Just be careful with articles like a or an before singular countable nouns.

Keep practicing and You're doing really well!