Change WordPress Texts

Hi there,

I want to edit this text “Hint: The password should be at least twelve characters long. To make it stronger, use upper and lower case letters, numbers, and symbols like ! ” ? $ % ^ & ).” and put other text like “test test test” , I found the original text in the po file, and I changed it but I know that If I update wordpress, the file will be replaced. What could I do? copy the po file to other location? but where?

Thanks in advance