'Initorcl' file missing
You need to create new parameter file,search for file alert_orcl.log ,open that file copy all parameters(only lines with "=" signs) after the line "System parameters with non-default values:" to a new file orcl.ora in any location e.g C:\orcl.ora 

Next start the database 

  startup pfile='C:\orcl.ora'; -- if successful go to next step
  create spfile from memory;    --create spfile 
  create pfile='C:\oracle12c\initORCL.ora' from memory --backup pfile


Always use rman to backup spfile and controlfiles.

Note:-You'll find alert_orcl.log in ORACLE_BASE\diag\rdbms\orcl\orcl\trace(start from diag folder in oracle base directory)