I think that URL fuzzing is what you are looking for. Pentest tools offers an easy solution, but they do ask that you have the rights to search. Probably to reduce hacking.Here is an online solution.
https://pentest-tools.com/website-vulnerability-scanning/discover-hidden-directories-and-files
Else download and install Kali Linux. Everyone thinks it is for hackers but if you are a professional website builder I think it will be good to have. Essentially, this question asks "how-to create" something like a sitemap, which most domains provide anyway.
Alternatively, try Arch Linux solutions.https://blackarch.org/fuzzer.html