Just bought a 10th generation iPad and a second generation, pencil, and a pencil will not pair with the iPadu

For the 10th generation iPad, you will need the first generation Apple Pencil.

Apple Pencil compatibility - Apple Support (CA)

For iPad10, you need a first generation Apple Pencil.

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.

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

See:

Pair Apple Pencil with your iPad - Apple Support

The first generation Pencil is charged and paired from iPad10 using the iPad charging cable - and an Apple USB-C to Apple Pencil Adapter:

New first generation Pencils now ship with this special adapter in the box along with the Pencil. However, some older stock purchased from retailers may lack the USB-C to Lightning adapter - and may instead have an older Lightning to Lightning Adapter.

For owners of older first generation Pencils, or for “old stock” new Pencils, the new special adapter can be purchased directly from Apple as an accessory.

https://store.apple.com/xc/product/MQLU3ZM/A