Mask a subdomain as subfolder and allow access from only from the folder URL


I have serviceX.example.com and I don’t want to move everything, I want to mask the URL so visitors and search engines see example.com/serviceX instead of the original/real location.

I don’t want serviceX.example.com to be accessible except from the masked URL with the subfolder.

The website is on a Linux server with Plesk installed on it.

How do I do that?