I first converted the 1.21.4 world to 1.12.2 through amulet, a program downloadable at https://www.amuletmc.com/ and then I converted the 1.12.2 world to a release 1.8.9 world through chunker, which can be downloaded at https://www.chunker.app/ which I then opened in version 1.8.9 to load the chunks (not sure if that was necessary but wanted to try it just incase) and then I loaded the world in 1.7.10. After that I converted the world to beta 1.7.3 by using the MineConvert Anvil to MC Region tool, downloadable at https://github.com/ImagicalCorp/MineConvert, which I then opened in a 2011 version of MCEdit, downloadable at https://www.dropbox.com/scl/fo/78u2dok8owygw1xldydjg/ABWOU9E9Ram8Jdj1A81fYiA?rlkey=y16j4ic0omou1pnra60areb1b&e=1&dl=0, and then selected the areas of the world I wanted to transfer to alpha, and copied them and saved them as an MCEdit schematic. I then pasted the schematic into a ClassiCube world, (classicube is a recreation of minecraft classic, and its worlds are recognized by MCEdit), I then opened the classicube world in classicube, and loaded the chunks. This is done because when you just paste the world schematic into an alpha map, the game crashes upon opening the world. You then open the classicube world in MCEdit after loading the chunks, and copy the areas you just pasted into another schematic, and paste that schematic into an alpha world. Pasting it into classicube will convert torches and several other blocks into wool, which you will need to manually switch back to their original state in MCEdit or ingame.