How we can check Our Dbs is running with spfile or pfile. Here is the some method to can find your file locations etc.
1. By using SqlPlus, Let us check your db started via spfile or pfile
$ sqlplus / as sysdba


SQL> SELECT DECODE(value, NULL, 'PFILE', 'SPFILE') "Init File Type" FROM sys.v_$parameter WHERE name = 'spfile';

Init F
------
SPFILE

As you can see our database started with SPFILE

So where the file?

SQL> show parameter spfile

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string +DATA/your_db_Sid_here/spfile_sid.ora

PS: If you are not usign ASM than your output will look like below:

SQL> show parameter spfile

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string /$ORACLE_HOME/dbs/spfile_sid.ora

2. If you are using ASM than try below find command

$ asmcmd find --type PARAMETERFILE '*' '*'
+DATA/your_db_Sid_here/spfile_sid.ora

3. From alert.log

[oracle@hostname~]$ cat alertSIDlog | grep "parameter setting"
Using parameter settings in server-side spfile +DATA/your_db_Sid_here/spfile_sid.ora