User certificate validation chain

As a datalake provider in SmartBuilding, we want to use certificate authentication for database users in Atlas.
When we create a user, we are able to download the certificate and the private key.
However, in order to be used by our software, we need all the certificate chain and not only the user certificate. Unfortunately, we are not able to find the issuer certificate and therefore the rest of the chain.

This is the issuer when we create a X.509 user.
Where could we find all the certificate that are parts of the validation chain ?

Thank you very much,