Seagate External PC to Mac Troubles

[CraigT54]

I am switching to from PC to iMac and plugged my Seagate External drive into the new Mac. It told me I needed to do some prep work and first offload all of the drive to my old PC before reinitializing with the iMac.

PROBLEM: When I plug it into the old PC, it recognizes that a drive is attached but doesn't welcome home an old friend. Rather, it asks me if I want to format. WHOA.

How do I get the old PC to recognize the external drive it grew up with?

How do I get around this "DO YOU WANT TO FORMAT? screen and get to the data on the hard drive. The drive was working fine last it was used in recent weeks. Thanks, Craig