Problem in SSL

Hi..
Thank for creating this plugin happy to user it.
I had a problem as my website is SSL secured that is https://gateonlinetest.com
but i am geeting an error that

Mixed Content: The page at ‘https://gateonlinetest.com/’ was loaded over HTTPS, but requested an insecure stylesheet ‘https://gateonlinetest.com/wordpress/wp-content/uploads/titan-framework-mobmenu-css.css?ver=4.7.1’. This request has been blocked; the content must be served over HTTPS.

I want to know from where I can change the http to https of this css call.
I want to know in which file it is being called.
Thanks