Is there a way to convert HTML to Coldfusion?

Since HTML and CFML are 2 different things (CFML generates HTML), the easiest way to do this is to do a massive extension change from .html to .cfm (this will make it so that when the page is requested, it is passed off to ColdFusion to be processed)

At that point, you can use the application.cfc to wrap the call to the requested page in <cfoutput> tags. A ColdFusion page could handle the file renaming.  Something like this (check it before you run it)

<cfdirectory

          name="htmlFiles"

          action="list"

          directory="#expandPath( '/absolute/path/to/root/html/folder' )#"

          filter="*.html"

          recurse="true"

          type="file" />

<cfloop query="htmlFiles">

          <cffile

                    action="rename"

                    source="#directory##name#"

                    destination="#directory##listFirst( name, '.' )#.cfm" />

</cfloop>