The maximum number of USB ports can be created in Windows is 256 ports (in theory).

But reality is 127 ports, so about 31 units of MOBITEK Q24 STK Modem Hubs. So 124 SIM cards per server.

But 1 server has maximum of built-in 6 USB ports, so 6 Hubs x 4 = 24 SIM cards per server.

We suggest that you use MOBITEK Q24 STK Modem Hub, model: STKMH-EP432-C which is based on LAN connectivity to overcome USB port restriction on a server.