Where is the Windows Phone App for Mac and how do I update it?

I upgraded to El Capitan the day before yesterday and now my Windows Phone App for Mac doesn't detect my Windows 8.1 phone. I am now unable to sync my phone or even detect my phone through Find My Phone.

Everywhere I search I get the advice "The Windows Phone App for Mac is available form the Apple App Store". I have never been able to find it. Has anyone? It automatically installed when I got my new phone at the beginning of the year after this happened with my Win7 phone and I ended up with a phone memory full of photos, videos and data I couldn't sync.

Overtime there is an update I lose the use of my phone and my settings keep reverting to default. I also keep getting asked to download and update my Java. I don't have Java and I can't seem to get rid of that annoying message permanently.

First my iMac says it doesn't recognise photo and video formats so won't import them, now it doesn't even see my phone. What next?!

I can't afford to keep replacing my phones just to have them work with my computer and I sure as shoot can't afford an iPhone (though I wold like one).

Any advice would be welcome. Helpful advice would be heavenly!

Jules