For the issue I was trying to solve, I knew which Column this value would appear in. It is also the entire contents of the cell that I need to replace.
After searching for 'python panda find and replace a value' I found this post https://www.geeksforgeeks.org/python-pandas-dataframe-replace/
This suggests
However this didn't work for me. What did work was to name the column specifically and to use 'str.replace', as mentioned here
https://stackoverflow.com/questions/53141072/replacing-column-data-with-pandas-replace-not-working