If you are looking for audio templates, I suggest you check the Adobe Audition application if you have one. The easiest way, in my opinion, would be if you record the necessary sounds and use the slow-motion effect on the recording. Still, you can try to use sounds from the applications like PowerPoint or different slideshow maker services like
https://www.fastreel.com/slideshow-maker.html. You can edit sounds and add the slow-motion effect with the proper audio editor. If you wish, I can share with you my library of sound effects, and maybe you will find something useful, let me know if you are interested.