You need to use Diskpart to clean all partitioning information off the card before you can connect and use it properly in WinUAE.
Run Diskpart as administrator, type "list disk" and find your card and select it, f.ex "select disk 3", then type "clean". Make sure you get the right disk, as you won't be able to recover any files after cleaning it.
If Diskpart says it succeeded with cleaning the card then it's ready for use in WinUAE. If Windows asks to initialize or format the card, click no/cancel.
Run WinUAE as administrator and load a quickstart A1200 config, enable turbo floppy, add the ClassicWB HDF file on UAE controller, and add your card as a new hard drive on IDE. Now you can finish the installation and reboot into ClassicWB.
Do you know how to use HD Toolbox or HDInstTools to change filesystem and partition the card correctly?