floppy disks

Good synopsis here:

https://lowendmac.com/2016/floppy-disk-compatibility-and-incompatibility-in-the-mac-world/

Older 400K or 800K disks are inaccessible unless you have a Mac floppy drive from that era to read them. In other words, you need an old Mac to copy the data off, then send it to your current Mac.

Only 1.44 MB disks can be read directly using a USB floppy drive.

Iomega used to make a floppy drive that used 3.5" disks commonly used by early Macs, but the Iomega disks may not work because the drive required installing Iomega's proprietary driver. Unfortunately, your description is too vague to be meaningful to me.

Supposedly there is a floppy disk that connects via USB. System 7, as I recall, used Mac OS format created using the then old disk formatter that came with System 7.

Have you checked for a Sierra compatible driver? Contacted Iomega Support?