How to tell if tightVNC client is installed on a linux machine?

Trying to log on to a Ubuntu Linux server using PuTTY and find out if TightVNC client is is installed on the linux box.
The  linux box is on a small peer-to-peer network with a couple of Win-10 PC's.
The Win-10 PC's have TightVNC server on them and we normally access them remotely through the Linux box by using a Win10 laptop with MobaXterm setup on it.

Guy who set this up is gone.
I want to skip MobaXterm and use PuTTY to log on to the Linux box.
I can in fact log on to the Linux server using PuTTY on the off site laptop... but what to do next is the basis for the 4 questions that follow...

First Question:As I understand it...- the Win10 PC we want to access is running VNC server- the other PC is running VNC client... right?
Second Question:In this case would the Linux box be running the VNC client or would I need VNC client on the laptop at my off site location?

Third Question:As I can now log on to the Linux command line using PuTTY... is there a command I can run to see if the Linux box has the VNC client on it?
Fourth Question:If the Linux Box is running VNC client, what command line instruction would I give it to launch the VNC client interface so that I can instruct it to connect to the VNC server on PC-1 on the local network?
Remember, I'm remote using a Win10 laptop and connecting via PuTTY to the Linux Server which is on the same local network with the 2 PC's each of which has the VNC software on them.
I'm new to all this so thanks for your patience and assistance.

Fran

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