Portal troubles

This is on 1.12 on bedrock. This website isn’t updated. I used to play on Xbox 360 version. When I got an Xbox one I converted the 360 world to Xbox one version then the Xbox one version to bedrock. I've been trying to make new portals in the original Xbox 360 generated land, but when I do, they don't sync up correctly. If I build one in the over world it'll be no where close to where it should be in the nether. For example if I build a portal at 320, y, 70 the coordinates in the nether will be 140, y, 33. If I divide the over world coordinates by 8 and build a portal there, it makes a new one in the over world somewhere far away. If anyone has a solution to this problem, please help.