Yes, you can authenticate users against your ADFS, this is done by adding your ADFS instance as an Identity Provider (IDP) in your okta org.
I would recommend reading through this article which outlines the capabilities of this configuration and steps on configuring the IDP. https://help.okta.com/en/prod/Content/Topics/Security/Identity_Providers.htm?cshid=Security_IdP#Security_IDP
If you require technical assistance in configuring the IDP I would recommend opening a support ticket so we can better assist you.
Following up on the above - Once it's configured then can the users from partner org can log-in with their fqdn? suppose my org is "mycompany.com" and partner org is "mypartner.org". After inbound saml config, user's from partner org can login with mypartner.org credentials?