No. The first generation Pencil is not compatible with the iPad mini6.
The first and second generation Pencil use an entirely different pairing and charging interface. The second generation Pencil can only be used with iPad models that have the magnetic/inductive dock that is exclusively designed for the Pencil. Charging is controlled via the iPad magnetic dock.
The first generation Apple Pencil uses the physical Lightning port for both pairing and charging the first generation Pencil. This pencil can only be used with compatible iPad models that have a Lightning connector.
In summary, the Apple Pencil models are not interchangeable - and can only be used with the iPad that has appropriate internal hardware.
Here is the definitive compatibility list for Apple Pencil and iPad:
Apple Pencil compatibility - Apple Support