How do I pair a first generation pencil with I pad pro if the connections are different?

The first generation Apple Pencil is not compatible with current models of iPad Pro, iPad Air5 or iPad mini6 - all of which have a USB-C port and a magnetic/inductive charging dock for a second generation Apple Pencil.

The two models of Apple Pencil are not interchangeable. Here is the definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

You don't.

The 2020-2022 iPad Air models, as well as all 2018-2021 iPad Pro models ALL use the newest, more expensive 2nd gen Pencil.

Both versions of the Pencil charge and pair differntly with their compatible iPad models.

Sorry and Best of Luck to You!