How to create key file and certificate file from pfx - Openssl

Install the Windows version of Openssl from:
https://slproweb.com/download/Win64OpenSSL-3_1_2.msi

Open a command prompt window in c:\Program Files\OpenSSL\Bin
(or even better, add Openssl to your Path)

Then type:

For the key file:
openssl pkcs12 -in [yourfile.pfx] -nocerts -out [keyfile-encrypted.key]
Example:
openssl pkcs12 -in c:\temp\mycertificate.pfx -nocerts -out c:\temp\keyfile-mycertificate.key

You will be asked for the pfx password (import password), and then asked to enter a password for the .key file (PEM pass phrase)

For the certificate:
openssl pkcs12 -in [yourfile.pfx] -clcerts -nokeys -out [certificate.crt]
Example:
openssl pkcs12 -in c:\temp\mycertificate.pfx -clcerts -nokeys -out c:\temp\certificate-mycertificate.crt

You will only be asked for the pfx password (import password) since the private key will not be exported.

And for .pfx to .pem

openssl pkcs12 -in file.pfx -out file.nokey.pem -nokeys 

openssl pkcs12 -in file.pfx -out file.withkey.pem

Convert x509 to PEM

openssl x509 -in certificatename.cer -outform PEM -out certificatename.pem

Convert PEM to DER

openssl x509 -outform der -in certificatename.pem -out certificatename.der

Convert DER to PEM

openssl x509 -inform der -in certificatename.der -out certificatename.pem

Convert PEM to P7B

Note: The PKCS#7 or P7B format is stored in Base64 ASCII format and has a file extension of .p7b or .p7c.
A P7B file only contains certificates and chain certificates (Intermediate CAs), not the private key. The most common platforms that support P7B files are Microsoft Windows and Java Tomcat.

openssl crl2pkcs7 -nocrl -certfile certificatename.pem -out certificatename.p7b -certfile CACert.cer

Convert PKCS7 to PEM

openssl pkcs7 -print_certs -in certificatename.p7b -out certificatename.pem

Convert pfx to PEM

Note: The PKCS#12 or PFX format is a binary format for storing the server certificate, intermediate certificates, and the private key in one encryptable file. PFX files usually have extensions such as .pfx and .p12. PFX files are typically used on Windows machines to import and export certificates and private keys.

openssl pkcs12 -in certificatename.pfx -out certificatename.pem

Convert PFX to PKCS#8
Note: This requires 2 commands

STEP 1: Convert PFX to PEM

openssl pkcs12 -in certificatename.pfx -nocerts -nodes -out certificatename.pem

STEP 2: Convert PEM to PKCS8

openSSL pkcs8 -in certificatename.pem -topk8 -nocrypt -out certificatename.pk8

Convert P7B to PFX
Note: This requires 2 commands

STEP 1: Convert P7B to CER

openssl pkcs7 -print_certs -in certificatename.p7b -out certificatename.cer

STEP 2: Convert CER and Private Key to PFX

openssl pkcs12 -export -in certificatename.cer -inkey privateKey.key -out certificatename.pfx -certfile  cacert.cer

Or:

openssl pkcs12 -export -out domain.name.pfx -inkey domain.name.key -in domain.name.crt

Or with intermediate and root:
openssl pkcs12 -export -out domain.name.pfx -inkey domain.name.key -in domain.name.crt -in intermediate.crt -in rootca.crt