Preferred method for removing mold & mildew from album covers

How about putting baking powder on them - I’m sure it will the mould

Is go-gone liquid for mold testing is available online also ?

I would throw them all away. Even if you somehow manage to clean them, you will never be sure that there is no mold left there. And that's the kind of caca you don't want to keep around.

Good suggestion whart.  I'll be doing this.

The other alternative is to not worry about the covers for now, and buy some high grade plain cardboard jackets- I like the white ones with the cut out in the middle sold by sleeve city. I use these in connection with new inner sleeves for repacking some records after cleaning. If you want you can write on the jacket in indelible marker or use a sticker (i do the latter) to better identify what’s in it. They offer pretty good protection as well. Mine are usually then bagged as part of a larger package for each record, but you don’t have to be obsessive about it. 

Check out eBay - your source for album covers in great shape and LPs inside in crappy shape.  Good luck.

I've replaced quite a few covers surfing in good will or similar stores. For smell you can use Ozzium. The way it works that you should place your smelly items let's say inside your car or bathroom sprayed all over with Ozzium and than close the doors for 20...30min. The car would work best
With goo-b-gone I cleaned large number of album covers as part of my business. Nothing work best there.

If you do a little research on the archival preservation of documents, books and paper products, you should find some suggestions for dealing with album jackets. I don't know how effective some of the methods are, or whether they risk damage to the colors or finishes of the jackets. (My suspicion is that many archives would probably start with fairly mild approaches that may be insufficient). There is considerable literature on this. Let me know if you cannot find it.

In the meantime, I would keep the records far away from the contaminated jackets, and even if 'treated,' keep the contaminated jackets away from other records/jackets or other materials in your home on which the fungus can grow. 
Let us know what you find. 

I suspect you will actually do more harm than good trying to clean the albums.  The best course of action is to try and replace the covers.  Otherwise, I'd leave them alone.  

use go-gone liquid.