If the default Distribution Point (DP) sites are missing from IIS after upgrading the OS of your site server, you can try to recreate them using the following steps:
Open Internet Information Services (IIS) Manager on your site server.
Expand the server node and navigate to the "Default Web Site".
Right-click on the "Default Web Site" and select "Add Virtual Directory".
In the "Add Virtual Directory" dialog box, enter "SMS_DP$" for the Alias and browse to the location where you want to store the DP content.
Select the "Read" and "Log visits" checkboxes and click "OK" to create the virtual directory.
Repeat steps 3-5 for each of the missing DP sites, using the appropriate Alias for each site (e.g. SMS_DP1$, SMS_DP2$, etc.).
Once all the virtual directories have been created, restart the World Wide Web Publishing Service (W3SVC) and the SMS_EXECUTIVE service.
After completing these steps, the default DP sites should be re-created in IIS and ready to use. However, keep in mind that these sites will need to be configured properly in the Configuration Manager console before they can be used for content distribution.