Erasing all the data from iPhones 5S and X

Good morning: so I have several old iPhones (5S, X), and presently I am using a 13 Pro. I have donated these old phones to my sister but when I specifically turn on the X, it of course, requests a password, which I did not remember. I decided to use the same pwd (just in case), I am using now. It opens up. What I need is to clear all the data from said phones (5S & X) so that I do not have to worry that my present data can be erased and also to make them clear/clean and available to the user (my sister). The iPhone X has info up to the year 2021, which I do not want to update because it will probably erase all my 13 Pro data. I understand that perhaps while using the corresponding IP address, supposedly, when erasing the data, it will not interfere with my new one, or does it?