What does you file look like in an editor? If it has a line such as -----BEGIN PRIVATE KEY----- then it is a PEM file. If it's a load of gibberish it's a .p12. Note that a .p12 is normally encrypted and requires a password to decrypt it.
What does you your file look like in an editor? If it has a line such as -----BEGIN PRIVATE KEY----- then it is a PEM file. If it's a load of gibberish it's a .p12. Note that a .p12 is normally encrypted and requires a password to decrypt it.