Can Apple Pencil 1st Gen magnetically attach to iPad 6th or 7th Gen?

No. The Apple Pencil Pro and second generation Pencil can both pair and charge with compatible models of iPad using the iPad's magnetic/inductive charging dock.

While the low cost USB-C Pencil can magnetically attach to iPad models that incorporate the magnetic charging dock, this Pencil can only pair and charge by using the iPad's charging cable plugged-in to the host iPad.

The first generation Pencil has no magnetic coupling at all - other than the magnet that retains its cap to the Pencil.

You can find more information about pairing and charging the first generation Apple Pencil here:

Pair and charge Apple Pencil (1st generation) with iPad – Apple Support

Apple's definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

No. There is no magnetic pencil connector on either iPad. The Pencil charges and pairs via the iPad's Lightning port on both iPads.

click here ➜ Pair and charge Apple Pencil (1st generation) with iPad - Apple Support