Convert CRT to PEM:
openssl x509 -inform PEM -in servername.crt > servername.pem
Convert KEY to PEM:
openssl rsa -in serverkey.key -text > serverkey.pem
Convert PEM (.pem, .crt, .cert) to PFX/ P12:
PS C:\OpenSSL\bin> .\openssl.exe pkcs12 -export -out newcertname.p12 -inkey originalcert.key -in cacert+certkey.crt