Hello @Hazem Elsaiegh Thank you for reaching out to Microsoft QnA Platform. I would like to state that if you already have an existing AD FS infrastructure and are performing a swing migration to new version of Azure AD Connect, then you can leave "User Sign-In" option to "Do not configure". This would not impact or make any changes to your existing ADFS architecture. Which means your user sign-in would flow through ADFS as expected.
I hope this helps and fixes your issue. Please "Accept the answer" if the information helped you. This will help us and others in the community as well.