What is the tactic a Scrum Master should use to divide a group of 100...

According to the Nexus Guide2, which is a framework for scaling Scrum, one way to form multiple Development Teams from a large group of people is to ask them to self-organize into teams based on dependencies, skills, domain knowledge, and personal preferences. This approach respects the autonomy and empowerment of the Developers and allows them to choose how they want to work together.

References: Nexus Guide