Good afternoon, today, and while trying to replace the light on the side mirror, I couldn't pull out the wire since as you can see the plastic piece which holds the wire in was already out and while trying to fit it back in to pull the whole thing out the wire snapped off. I don't think I can just replace the mirror since the wires are coming out of the car it self what should I do? The lights on the mirror were working before the cover was broken hence the replacement.

 

Remove mirror, splice in new wire. The connector is available from Mercedes. No, I do not know the part number; you can look it up on the electronic parts list, inquire if someone on this forum can look it up for you, or let the dealer parts department look it up for you. If the socket on the light assembly is bad, bite the bullet and replace the light assembly.
Not much else one can do about it.
EDIT: one other option, obtain the connector from Mercedes, carefully cut off old connector with diagonal cutting pliers without damaging the wires, insert pins into new connector. Upon reflection, this is the route I would attempt first.

 

Would buying a used side mirror in order to extract the required parts from it be a good idea? I am currently searching for the individual parts.

(I mean a whole mirror assembly)

 

https://findpigtails.com/?

 

The problem is fixed I bought a connector piece with it's pins I cut off a piece of the old wire and spliced it, then I inserted it into the pin and closed it on the wire after which I inserted the 2 wires into the connector.

@bbirdwell, the pigtail website is something I will be using it for other stuff. Thank you for your responses I appreciate it.