Save a certificate on Microsoft IIS8.X/10.X and Windows Serveur 2012/2016

Recommended method

Open the Windows launch tool with Run or from the run menu with the keyboard shortcut Win+r. Then, type mmc and click on OK.
Click on the File menu then on Add/Remove Snap-in.
Click on Certificates then on Add.
Select your currentaccount type (Windows) then type in the requested informations based on your account type.
Accept by clicking on OK.
You can now unwind the Certificatesmenu to view the store containing your certificate ( Personnal by default) and its sub-folder Certificates. You should be able to see your certificate.
Right click on your certificate and select the menu All Tasks - Export.

Click Next
Select Yes, export the private key then click Next.
Make sure the box Include all certificates in the certification path if possible is checked. Then, click Next
Check the box Password, then type in the certificate's password.Next.
Choose a directory and a certificate name, then click Next.
Click Finish to confirm your certificate export

Attention: we cannot guarantee that this method will correctly export certificate chains.

Open the Internet Information Services (IIS) Manager from the Administrative tools
Select your site from the Server Certificates option.
Then select your certificate and click on Export from the Actions menu on the right hand side of the window.
Right click on your certificate then click on View.
Click on the Details tab and then on Copy to File

Click on Next
Select Yes, export the private key then click on Next.
Make sure the Include all certificates in the certification path if possible is checked then click on Next
Check the Password box and enter the password protecting your certificate and click on Next.
Select a file and a name for your certificate then click on Next.
Then click on Finish to validate your certificate export.