Add new Wireless network and redirect internet to USB modem

Hi
I have a little Mikrotik experience and have been searching around without finding a solution yet.
I have a hAP ac lite at home that primarily connects to the internet via a ethernet cable (that comes from my Huawei LTE Router) and broadcasts it via WiFi (eg. Home). I have also plugged in a 3G USB modem that I can use in case of failure of the LTE, which works if I unplug the LTE router. However, I would prefer to redirect the USB Modem’s Internet to be broadcast via a separate Wireless Network (eg. Home_3G). How do I go about creating a new WiFi Network and redirecting internet to route via 3G Modem?
Thanks

What USB modem is it (vendor, model etc)?