I have cold. Which medicine should I get?

Symptom relief... Colds are usually due to a virus so antibiotics are ineffective. It will resolve on its own so all you need is meds to relieve your symptoms while it runs its course.Example, Acetaminophen to reduce fever and body aches, saline nasal spray to relieve stuffy nose, etc. You should feel better in a few days regardless.
Treating a cold. The over the counter (otc) medicine you take for a cold depends on what cold symptom is bothering you the most, and what other medical conditions you have. There are too many options to tease out in this setting. Best to speak to the pharmacist at your preferred pharmacy for the most appropriate medication or medication combination.