Depending on your build model year early MacBook version a possible
choice may be El Capitan 10.11.6 from the installer download link here:
• How to download OS X El Capitan - Apple Support
There are products listed with their model details to indicate what may
be a match. And if there were any last updates for Snow Leopard 10.6.8
those should appear if you run software update. A few last compatibility
updates were available to allow Mac App store integration, for upgrades.
If your computer product could run Yosemite and you didn't buy or get
that upgrade when available, you should be able to get & run El Capitan.
There may be other required hardware upgrades to the Mac to use this.
Additional software downloads may present themselves from App Store
after arrival to a running El Capitan; such as later security and safari.