Renewal of third party SSL

Hi all,

I am helping with an existing site which I did not design. It currently has a third party domain connected.  The DNR has stated we must renew the SSL to avoid a "not secure message".  I know squarespace offers SSLs - is there any way I can check to see if the site is using squarespace's SSL or the third party's SSL?  If it is using the third party's SSL, do I need to "reconnect" the website with the new SSL information?

Thank you in advance!

Thank you!  Very helpful!