Super basic noob-level question about graphics in iOS

I'm 74 years old. My35 year-old son and I are developing a game

Well that’s the coolest thing I’ve encountered today!

I understood that I would need to supply 1x, 2x, and 3x versions

Actually no modern device uses 1x density, so you really need only 2x and 3x versions. Here’s a handy chart: https://www.ios-resolution.com

Wouldn't any device accessing the 3x versions of the graphics all have blurry elements?

Yep, the device will render exactly what you give it, if not resizing the image further or applying any other transformation. So you definitely want your image assets to look as good as possible at design time.

created all the elements at that largest size, naming it the 3x version, so that subsequent 2x and 1x versions would be reductions

Downscaling is probably better than upscaling, but for best results you may want to draw the artwork by hand for each density. The same image at each density will be roughly the same physical size on all devices, but the 3x density lets you provide richer detail. Or look into supplying vector assets, if that meets your needs.

Thank you, Scott. I really appreciate your help with this!