Can I use a Apple Pencil 1st Generation with my iPad?

Look at the system specifications for the Apple Pencil, it will tell you the devices it will work with. Next, then please read which iPad models it is compatible with and then look in the About section of the Settings app for your iPad to learn which iPad version you own.

Here is Apple’s definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

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 of the Pencil and host iPad for both pairing and charging the first generation Pencil. The first generation Pencil can also be charged using an inline charging adapter and the iPad’s Power Adapter. This pencil can only be used with compatible iPad models that have a Lightning connector; with the sole exception of the new iPad10, requiring a special adapter, iPad models that feature a USB-C port lack any means by which to pair with a first generation Pencil.

The new Apple Pencil Pro can only be used with the iPad Pro M4, iPad Air M2 and new iPad mini (A17 Pro). Apple's USB-C can only be used with iPad's that feature a USB-C charging connection.

In summary, the Apple Pencil models are not interchangeable - and can only be used with the iPad that has appropriate internal hardware.