Hmm. You're wandering in a gray zone here as not all iOS apps are designed to work on macOS.
In this case, the iOS app for Stardew Valley is not the same than the one you can usually install on a Mac through GOG or Steam. This means that the way save files are managed is also different.
Thus, the save folder path you indicated in your post is the one for the desktop application (GOG/Steam) and because this one is assumely not installed on your computer, this folder does not exist.
What I would suggest is to launch the iOS Stardew Valley app you've installed on your M1 Mac and start a new (dummy farm) and save as soon as you can. Then, exit the game and search for the most recently updated files on your drive that match your dummy farmer's name, that will tell you where the iOS app is storing its data. You can then copy your iPhone/iPad save to the correct directory and you shoud be able to use it to play.
