Convert certificates like pfx,cer or p7b to pem using openssl

pfx to pem
openssl pkcs12 -in cert.pfx -out cert.pem -nodes

cer to pem
openssl x509 -inform der -in cert.cer -out cert.pem

p7b to pem
openssl pkcs7 -in cert.p7b -inform DER -print_certs -out cert.pem