SQL instances running a lot of databases can get a bit confusing as to what is kept where. Especially if said instance was setup by someone else in times prior. To that end, there is a very handy query you can run in SSMS to quickly return the on-disk file locations of all SQL data files. You can use this query exactly as-is with no modification:
This will output a nicely formatted table including filename and folder path, including the Master database and Temp Database files.