Download: https://github.com/jaquadro/NBTExplorer/releases
Alternatively NBT Studio is much faster and cleaner but works the same way https://github.com/tryashtar/nbt-studio/releases/
1.a If you are crashing due to an entitiy or tileentity the crashlog might contain the exact coordinates
1.b If you have a waypoint there for example checking your map files can be helpful
1.c If your player is in the same chunk you can look up your players position