1.
If you are using the Desktop application, then you can use
Plain File Mode and set
Extension: Override.
2.
If you are using the command-line, then you'll want to use a simple shell script:
https://unix.stackexchange.com/a/149725
"volume1" suggests that you're using
Synology NAS. Debian tools such as
rename and
inotifywait that we would typically use for this kind of use case might not be available. However, the solution in the link above only uses
find and
mv so it'll work on any Linux machine, and we can then use
Synology Scheduler to call that automatically once a day.