Just bought a RB750Gr3 and new to RouterOS. I want to use with an LTE modem through USB connection. How do I get started?
To plug it in seems like good first step. Hopefully you bought something supported by RouterOS. And then this should give you some ideas: https://help.mikrotik.com/docs/display/ROS/LTE
Probably this list of USB modems could help: https://wiki.mikrotik.com/wiki/Manual:Peripherals or https://help.mikrotik.com/docs/display/ROS/Peripherals