MacOS Recovery cannot proceed

Hi!

I have an old MacBook Pro 2009 and I need to format it.

So I started Recovery OS X but it's not able to proceed cause it needs OS Mavericks and issues an error (I suppose cause Mavericks is no more downloadable from app store).

So now, I'm able to do nothing, no way to exit from recovery and no way to go on cause I don't find an OS to download and to load on a USB.

May someone can help me? Is there a possibility to come back?

In the app store, into Purchased section, there is no Mavericks installation, maybe cause it wasn't dowloaded with my appleId.

Thanks,

Silvia