Hi and welcome to the forum,
I never heard of Anna34 before your post, so I searched on YouTube and found her. I don't think that she's selling her products, because she writes there that nothing of her shows is actually made by her: not the styles, and not the graphics. She states (in Russian, that I had to translate) that she found everything on the web for free (??), and that she put everything together in ProShow.
So, you might just want to contact her through her YouTube channel. Just send her a message.
But, I'd like to answer your second part of the question, and also something that you didn't actually ask
ProShow Producer comes with built-in slide styles, transitions and also templates, that you can use in all your shows.
Also, Photodex, the makers of ProShow, sell additional packs of effects.
And, also in addition, there are several 3rd party vendors, (and I am one of them), who sell such effects on their personal web sites. This forum has a separate section named "ProShow Marketplace" where we advertise our products from time to time.
And, moreover, there are even more effects that are distributed freely on the internet, from various sources. I don't know about the quality of these free products, but you might have some language problems while using them. Also, not everything that is distributed freely, is really free. There are copyright issues that need to be addressed.
And now, to that "drawing effect" that you liked.
There is something in ProShow Producer that is called "layer transition". It is pretty much like the transitions (the effects) that you apply between the slides of your show, only they work on just one layer of the slide - a picture, a frame or some other graphic that you might have in your slide.
So, if you have a picture in your slide, and instead of that "Cut" transition,that you see at the beginning of the timeline, you apply the "Paintbrush" transition, it will appear as if your picture is being painted.
If you want a bit of "sophistication", you can use a frame and mask, and by means of keyframes, you can make the frame come into the slide a few seconds before the picture, and then make the picture appear through a different effect.
For short, something rather simple, but nice