Updating Minecraft 1.13 to Minecraft 1.14

I’ve been playing for awhile now and I have a specific world that I just wanted to update to Minecraft 1.14. The only problem here is that the seed used to generate the world is in Minecraft 1.13 pre release 8, keep in mind… pre release.

So is there any way for me to update the world to Minecraft 1.14.3 without the unloaded chunks converting to new Minecraft 1.14 terrain? Cause that would ruin the whole map.

I also would like that the chunks outside the world border to have the newly generated terrain and stuff. If it adds context, the world that I’m trying to create is the well known hermitcraft 6 world with the 1.14 area.

The seed is -786123897547630675894, and the world border is just /worldborder set 4122.