There are many examples on the internet. Review them and find one that suits your needs.
https://www.bing.com/search?q=powershell+find+and+replace+text+in+file
Some examples here: https://stackoverflow.com/questions/2837785/powershell-script-to-find-and-replace-for-all-files-with-a-specific-extension
If you are new to Powershell, here is a good reference.