Is it possible to create a Chrome extension that would transform individual elements of an already loaded page?

Question

Browser extensions

I've been trying to find something similar for the second day, but it doesn't work. Maybe I'm asking the wrong question?
It is necessary that, being on the page of an American online store, where everything is in feet-inches, pounds-ounces, when you click on the button in the extension, for example, on the page, all values ​​\u200b\u200bin the Imperial system of measures are duplicated into those converted into grams-kilograms-centimeters-metric meters systems like this currency converter extension:
https://youtu.be/yqupriUQob0
The only solutions are when the information is displayed on a side popup page, usually called popup.html. And I would like the information to be displayed on an already loaded page, as in the video above.
Found that a similar question was asked here a few years ago, only there it was about highlighting all occurrences of the word on the page.
If someone understands the issue, please tell me where to dig. Just don't say that you need to study the DOM more seriously.

Answer 1

https://www.google.com.ua/search?q=chrome+extensio...
https://chrome.google.com/webstore/detail/converts...