2 Differents thank you page extension

I am monitoring the ‘Merci’ page in French for Google Ads, and I have noticed that three of my sites still use the ‘.php’ extension, while all the others use the ‘.html’ extension. I am puzzled as to why this discrepancy exists. Because this complicates the configuration of the conversion tracking in Tag Manager.

How can I change the 3 sites that are still using .PHP to be the same has all my others sites thank you page who are using .html?

Here’s the list of all my thank you page in french:

https://pmeagenceweb.com/merci.php

https://solutiongouttieres.com/merci.php

https://areleclerc.com/merci.php


https://ashmaconnerie.ca/merci.html

https://alarmeluma.com/merci.html

https://carolecharronavocatemediatrice.ca/merci.html

https://louisepoliquinavocatemediatrice.com/merci.html

https://nettoyagebioclean.ca/merci.html

https://saucissescompagnie.com/merci.html

https://solutionrenos.ca/merci.html