Hello KikiREE,
Thanks for reaching out to Microsoft Community.
We understand how important this setup is for your device.
In that case, if your monitor only has two Thunderbolt and three USB-C ports for input then, you could have gotten a minidisplay to USB-C cable for this setup. Note that Surface Laptop 2 only outputs display via minidisplay port.
To know more about this setup, please see Troubleshoot connecting Surface to an external display - Microsoft Support.
We look forward to hearing from you.
Regards,
StevenK