Q: What is the best way of designing a study that is assessing 3 or more companies?

My study will be assessing 3 or more companies on their view on supporting personal development of employees, and its effects on performance if given enough attention. Now, my problem is choosing the right study method and sampling design. My view is that, personal development affects each and every employee in the organization, therefore there's a high chance of any of them participating in the study which means using simple random sampling strategy. I am also thinking of using convenience sampling to choose the region where my study will be conducted from. Will I be correct?