You are free to use any version you like. Generally production application want to be on the highest available LTS, currently 9.12.5. See https://marketplace.mendix.com/link/studiopro/
Marketplace modules can get imported into application that have a higher version.
If the module is so much older that you get the message “...first import it into an Mx 8.18.12 application ...” then do that, then upgrade that app to 9.16.1, export the module from the upgraded app and import that exported module into your 9.16.1 app.