I have tried to clean only the regions that I don't use, without removing those that have buildings or areas that I don't want to be deleted, but since the regions are called "r.0,0 or r.120,-120" it is very difficult know exactly where you belong in middle earth.

For this I have tried to use programs that I have already used for other versions of minecraft such as "Unmined" but unfortunately it does not detect it.

Well, after researching for a while I found that the MCA SELECTOR 1.17.2 world editing program is capable of detecting this dimension and best of all, it tells you which block, chunk and region the explored area is in. the negative is that in order to go to certain parts you must enter the coordinate, you can drag with the arrows to explore your map in the program. to visit a specific area and be able to eliminate chunks or regions you go to "View>Go to" (or Ctrl + G) and put the X and Z coordinates. Then you can select the regions or chunks by left clicking (or dragging while pressing) and to deselect the same, but right click. you can delete it by pressing Ctrl + D and you should see the warning of how many chunks will be deleted, (1 region 1024 chunks).

I hope it can help you to lighten the weight of the map, either for a server with limited size or for your single player world

Links:

https://github.com/Querz/mcaselector

Windows version:

https://github.com/Querz/mcaselector/releases/download/1.17.2/MCA_Selector_Setup.exe

Universal Version:

https://github.com/Querz/mcaselector/releases/download/1.17.2/mcaselector-1.17.2.jar

(i use last version 36.14 for 1.7.10 forge)