You can use this 'Find Replace in Selection' (Dropbox download) Automator Quick Action (also known as an Automator Service). It contains a shore AppleScript.
Once the Quick Action/Service is installed, you select the cells where you want to do a find & replace (in your case select an entire column), choose Find Replace in Selection from your Numbers > Services menu, and follow the prompts.
To install just double-click the downloaded .workflow package. You may then need to give permission at System Preferences > Security & Privacy and make sure Automator and Numbers are listed and checked at System Preferences > Security & Privacy > Privacy > Accessibility. Installation should take less than a minute.
If you find you don't need it any more you can uninstall it just as you would any other Automator Quick Action/Service. In Finder hold down the option button and in the menu Go > Library > Services and delete the way you would any other item in Finder.
SG