Minecraft version of the mods change without harming the world?

I play Minecraft 1.7.10 with a lot of mods and now want to change the version from 1.7.10 to 1.12.2 but I have a few questions.

I play a world in Minecraft and I'm scared if I change the version of the mods that everything is gone in the world. So all things that I have built myself with the mods are then simply gone and can no longer be saved.

Can I just change the version of Minecraft and the mods and then continue to play normally as always in my world without problems?

Download world

Make a new server or change the version including mods

Reload the world