Simple ... get some more floppy discs
You CAN use 1.44mb labeled floppy discs in Amiga drives with no ill effects. The Amiga drive doesn't differentiate between both types and formats both to Amiga's880kb' standard.
ADF files are a track by track copy of an original Amiga game and cannot be loaded as per an original game
What you should buy is an external drive (DF1:) for your A500+ because it makes dealing with ADF files so mach easier