Can't move custom ringtones to Tones folder on iPhone 6S Plus

I created several ringtones from songs. I followed directions I found online that said to select the song in iTunes on my desktop iMac, create a start and stop time no longer than 30 seconds, save it as an AAC file, drag the file to my desktop, change the extension from m4a to m4r, then go to the Tones folder on my iPhone in iTunes and drag the file into the window. Unfortunately when I drag the file, it gets stored in Music and not in Tones and no matter what I do (drag, copy and paste, etc.), the file won't move.

Any suggestions? I'm running Mojave 10.14.5 on my iMac and iOS 12.2 on my iPhone.

Thanks,

Lloyd