$ file query.pem
query.pem: PEM RSA private key

$ ssh-add ./query.pem
Identity added: ./query.pem (./query.pem)

$ ssh-add -l | grep query
2048 ef:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX ./query.pem (RSA)

$ ssh-keygen -l -f ./query.pem
key_read: uudecode PRIVATE KEY----- failed
key_read: uudecode PRIVATE KEY----- failed
./query.pem is not a public key file.

-----BEGIN RSA PRIVATE KEY-----
MIIEp.... etc.

-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,E15F2.... etc.

$ ssh-keygen -yf path/to/private_key_file > path/to/store/public_key_file

$ ssh-keygen -lf path/to/store/public_key_file