I think I can upgrade my 2015 Vizio to HDR. Help me though please.

I'm sorry but looking into your question a little makes me believe that it is highly unlikely to work at all. Unlike computers for example, most TV's are not modular, meaning that you can't just desolder a few parts and throw in something new. On top of which HDR also requires specific firmware. If you manage to get a TV working from mixed parts, which already seems highly unlikely, even if the internals of the 2 models are highly similar, there is no saying the required software will be willing to run on it.

I'm sorry, but I'm afraid that this is an area where DIY'ing just isn't worth it. You're more likely than not to break your TV, and if you manage to get the parts, get them installed properly and have it all be compatible there is still a chance that the software won't run, meaning you still won't have what you wanted.

I know this is probably not the answer you were hoping for, and I wish you good luck with any ohter projects you may have.