To view the certificate Modulus:

openssl x509 -noout -modulus -in [certificate-file.crt]

To view the key Modulus:

openssl rsa -noout -modulus -in [key-file.key]

Command to compare certificate vs private key

$ certMod=$(openssl x509 -text -noout -modulus -in server.crt | grep "Modulus=") && \
	keyMod=$(openssl rsa -text -noout -modulus -in server.key | grep "Modulus=") && \
	[[ $certMod == $keyMod ]] && echo "Equal"

Tribut to Peter Mescalchin magnetikonline for the script above https://gist.github.com/magnetikonline/fbdb26fcb34ca5038c03507cbdfdb534