My Older Sites are Appearing " NOT SECURE" Any Tips

HI, I still have few sites with the older site builder, Years ago they had fix this issue? If so please respond if possible, Also I know we should just convert over to Website Builder, Once we create the new design and have that in place well do.  Does any one know how to clear up this SSL up on older site builder?

Also we have new site with Website builder and that is good to go.