As Rex and Pyro have mentioned, I believe the ships that you received 'free' were in fact the opportunity to purchase these ships in-game with game credits you earn, either from the day zero when you start out, or at a time earlier than the rest of us. The Cobra Mk IV was a freebie with Horizons IIRC but I can't say for certain, and the Eagle was something that people got if they backed the game before release.
Please don't quote me on either of those points as accurate though as I can't be certain given the time passed. However the point I wanted to make was:- as a 'Mercenary' edition backer, you have access to these ships far earlier than other players would have done, via the shipyards in the stations, or by the way you initially register your CMDR and setup the game. They can't be found placed around the bubble or the galaxy in a way meaning you can switch between them in different places; they are just there for you to move your CMDR in to if you choose to, at an earlier stage than other CMDRs. I had the same advantage with the CM4 on purchasing the Horizons season pass, but I still haven't got around to actually going to a shipyard in-game and choosing to move into the ship so I have no idea if I would like to fly it or not!!
I hope that makes sense?! And please don't think my post to be critical as it isn't in the slightest. I do hope though that you are able to get on with, and into the game, as I think you will adore it. As others have mentioned, the scope is becoming huge and details are flourishing but there are still many things FD plan to and want to do with the game

I do hope you will be amazed with the content improvements and additions to the game, and that you will enjoy as much as I do! Feel free to add me in-game as a friend if you so wish and I will gladly lend you a hand with starting out if I can, but I am sure you will be fine as you get going.
As always my friend, fly safe and enjoy the game; cheers,
The Hat
CMDR A.S.S hat [but with no gap between the S and h, or the filter will block my typing!!]
