How to simulate unique users hitting on different clients which all resides in the same instance

Gatling (Open-Source)
1

Gatling version: 2.13
Gatling flavor: Scala
Gatling build tool: maven

I am new to Gatling. I have to simulate the below case.
1 Single Server instance where the main application is hosted → Within the application, multiple clients and users can be created → 1 user will have access to 1 client. All the client authentications are different. How can I simulate a scenario using gatling, where 100 unique users are accessing 100 unique companies at the same time and measure the performance

2

2.13 seems like an outdate version.

Does 100 unique companies have different endpoint url ?
Does your users change company during the test ?