Auth0 to use 3rd party IDP for authentication via SAML

Hello All we have a request to integrate our store front on to another client portal which is having SSO configured.

Ask: When we add our storefront to the client’s portal, where the users are already getting authenticated by their IDP for SSO, they do not want another login prompt for their users when they click on our store front link

Here’s the assumed flow:
Users login to customers portal through SSO > Their IDP autheticates and users get access to content on the portal > Our storefront link will be hosted on the portal which when the user clicks > should allow them to connect to our store front

Our site supports OIDC and not SAML, we use Auth0 as our IDP currently.
so if the clients users should gain access to our portal how would Auth0 connect to 3rd party IDP and then allow access to our store front?

Could someone help with what the sequence of steps should be and what all inputs should we get from 3rd party IDP?