Adapter for Mini DisplayPort to a usb c hub for my MacBook Air?

Mini Display Port as its name implies would only send a video / display signal, so a USB hub would not work with it.

Do you mean Thunderbolt 2? Thunderbolt 3?

What exactly are you trying to do? What devices exactly are involved?

I have a similar issue. New Macbook Air that I want to connect to 10 year old Apple 36" monitor (that is in great shape). The monitor has 3 cables coming out (one powers old laptop, one is USB-A, third is monitor cable (miniport?).

looking for help to at least get the monitor to connect video from new USB-C port on new Macbook Air.

thanks for any help you can provide

USB-C Digital AV Multiport Adapter