My limit of connections is 100 users, but we have 9 servers. How can we increase the number of people at same time on our meetings?!

You need to reach out to your reseller and identify what licensing change needs to take place.

If you are using Named Host licenses, then you will either need to consider changing to Concurrent User or acquiring Webinar liceses for larger capacity.

If you are using Concurrent User licenses, then you will need to purchase more liceses or acquire a Webinar license for larger capacity.

The number of servers doesn't reflect your licensing limitations, but more about the ability for your system to handle concurrent connections of any type and failover functionaltiy.