you need BC_VUP3 to upload the firmware which is free from Uniden, there is a link from the firmware page.
Any modern Windows version works. If you have not kept the Windows updates current, you could have some Windows files to download.
https://info.uniden.com/twiki/bin/view/UnidenMan4/BCD325P2FirmwareUpdate
https://info.uniden.com/twiki/bin/view/UnidenMan4/BCD996P2FirmwareUpdate
Any modern Windows version works. If you have not kept the Windows updates current, you could have some Windows files to download.
https://info.uniden.com/twiki/bin/view/UnidenMan4/BCD325P2FirmwareUpdate
https://info.uniden.com/twiki/bin/view/UnidenMan4/BCD996P2FirmwareUpdate