This depends on what you are investigating.
Work Step by Step
The data set may be a population if you are simply investigating the salaries of pharmacists at a particular pharmacy. It is a population because you have investigated all o the pharmacists' salaries. However, if your aim is to find the average salary of a pharmacist in a certain country, regardless of which pharmacy they work at, then these salaries from a particular pharmacy are only a sample of the bigger picture.