I have a sharepoint site with 100's of documents. For each document a single value has to be selected from a choice column. I now need to change the names of the values in this column. I modified the column values but they do not propagate to the documents. When you create a new document you can choose the new value but old documents still have the previous value. I either have to edit each document and manually choose the new value OR write a flow/power automate process to do this for me.
I am in the process of writing the Flow but am completely stuck. The basics of what I want to do is replace the old value with the new value for each document. Please note that not all values need to be updated, only 2 of the three.
Example:
Column Name: Responsible Person (which is seen as '_x0043_ol1' in my screen shot)
Values: Choice A, Choice B, Choice C
New Values: Choice A2, Choice CB, Choice C
When I run this the error tells me that "Input string was not in a correct format."

I also need this process to go through all documents in the site and perform this action.
Any help would be greatly apperciated.