Azure Build Pipeline For IOS app

Merry Christmas

Guys, now I can manually build an IPA file signed with the a cert file and a provision file and further upload it to App Store. Now I want to test it on the Azure devop pipeline and let the pipeline do the building and upload it to appstore, but face following issue. The cert file that I generated has the extension of .cer, but the one from the pipeline is .p12 ? I am not sure if it is the same cert file and as for my .cer file, it does not have a password. The cer file is already uploaded to secure library, so it can be found.

• task: InstallAppleCertificate@2
  inputs:
  certSecureFile: 'something.cer'

Following is the build trace

Starting: InstallAppleCertificate

==============================================================================

Task : Install Apple certificate
Description : Install an Apple certificate required to build on a macOS agent machine
Version : 2.156.0
Author : Microsoft Corporation
Help : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/install-apple-certificate

==============================================================================
[command]/usr/local/bin/openssl pkcs12 -in /Users/runner/runners/2.163.1/work/_temp/ios_distribution.cer -nokeys -passin pass: | /usr/local/bin/openssl x509 -noout -fingerprint -subject -dates
45017636920D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1220:
45017636920D06C03A:asn1 encoding routines:ASN1_D2I_EX_PRIMITIVE:nested asn1 error:tasn_dec.c:788:
45017636920D08303A:asn1 encoding routines:ASN1_TEMPLATE_NOEXP_D2I:nested asn1 error:tasn_dec.c:720:Field=version, Type=PKCS12
unable to load certificate
43128029240906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:697:Expecting: TRUSTED CERTIFICATE
[warning]No P12 password was supplied. If the P12 file requires a password, the best practice is to supply it as pipeline variable and mark it secret by enabling the lock icon.
[error]Error: /usr/local/bin/openssl failed with return code: 1
[section]Finishing: InstallAppleCertificate

The tutorial that I am following is this one, please help.
https://docs.microsoft.com/en-us/azure/devops/pipelines/ecosystems/xcode?view=azure-devops

Regards
Marc