as its a very repeative tasks, I would use AI for it. Start slow: let AI transform one file and see results. Then create a memory.md for your manual changes, that the AI should remember. Let AI write evrything there, that you requested to change systematically so it remembers for the next files. Do that 3 times so that you upgraded 3 files in total. After that most of the issues are fixed. Then tell AI to format your codebase. It will do pretty quickly and pretty good