Detecting in time if a server certificate is expiring is one of the more important tasks in AWS. Unfortunately, many individuals struggle with this. The following will give you a list displaying all certificates and sort them by expiration date.
aws iam list-server-certificates \
--output text \
--query 'ServerCertificateMetadataList[*].[Expiration,ServerCertificateName]' \
| sort
To display the certificate of a specific stored item you can do:
aws iam get-server-certificate \
--server-certificate-name $certificate_name \
--output text \
--query 'ServerCertificate.CertificateBody' \
| openssl x509 -text \
| less