Field extraction on source type

[indeed_2000]

on splunk when i want to do field extraction ask me source type. and when I open this listbox show files on that path as source.

Here is the logs “/opt/logs”
On this path there are some other files that have different structure! For example config file, database export, ...

While when I import data also create specific new index for it, but this index not show on source type listbox.

Now i need to do field extraction on several log file that exist on that path.

Any recommendation?
Thanks

Thanks