Chunks?

(Sorry for my bad english)

Some time ago, I did a construction that cost me weeks of work.  I accidentally uninstalled Minecraft and my worlds were erased.  I had a backup of that world on my PC.  I reinstalled the game and exported the world ... I loaded the world and that build only had a small part of it and several holes in the grass ... What can I do to get my world back?  PS: I tested in Minecraft for Windows 10 and it is also the same.