Ліки is a mass noun. If you need to talk about any specific quantity you can say "(медичний) препарат" or "медпрепарат"
Ліки is a mass noun and is always used in the plural. English has words like this too. For example, bread and water are always used in the singular.
You mean "drugs" . . . You can use "Here are your drugs" but unless you are at a hospital or drugstore, that phrase could imply you are giving an illegal group of drugs to someone.