You will have the tenant ID, client ID, client secret and useful endpoints of your
application.
You can get your certificate keys from
https://login.microsoftonline.com/<tenant
ID>/discovery/v2.0/keys.
Send a POST request using Postman to the URL
https://login.microsoftonline.com/<tenant ID>/oauth2/token
with your client_id, client_secret.
The response from this POST request will be the access token and its properties.
This access token will be used to send a request to the JWT validation enabled REST
services.
Open the https://jwt.io/ website and copy the access token into the
Encoded text box.
You can get the kid value from HEADER properties in the
Decoded view.
Open https://login.microsoftonline.com/<tenant
ID>/discovery/v2.0/keys in a Web browser.
You can find the matched key with the same kid value as the
access token.
Copy the String value from the x5c field of the matched key and
save it to a text file.
Convert the text file to an azure.cer file, for example: