Minecraft, expanding map?

Does anyone know if I can get the map to expand in certain direction? I tried to expand my map and it kept going more down and to the right, leaving my base in top left of map.

I want to expand it and have my base more towards middle of it. Also if someone can get me a link to where I can learn some in game commands that would be great. I have Minecraft 1.14.4 in Java.