How can I convert a **point's position** to a **vector** which I can then use as the endpoint for an arc node?

I'm using the latest version of blender. 

First time using Stack Exchange, so let me know if you need more info.

Clarification: 
Is there an ideal way to extract the **Position** of a **vertice/point** into a usable vector to start a "Mesh Line" or "Arc" from?

[![Update attempt using advice from quellenform ][1]][1]


  [1]: https://i.sstatic.net/AlrYe.png