It depends if you would like to run performance testing or load testing only. But basically if you would like to get performance metrics 100 concurrent users should be enough assuming that nobody else is using the platform when you run such tests. 100 virtual users is equivalent to your 100 real users if your user paths stick to real user journey.

Now if you would like to know how many users your infrastructure/application can manage with an acceptable response time before eventually crashing then you can consider load testing with much more users.