https://github.com/dc42/RepRapFirmware/releases/tag/2.05
Upload this: https://github.com/dc42/RepRapFirmware/releases/download/2.05/Duet2Firmware-2.05.zip
That will update the main firmware, wifi server, and DWC.
Then upload the combined firmware, and DWC 2.07 from here: https://github.com/dc42/RepRapFirmware/releases/tag/2.05.1
That will get you up to speed.
Read the release notes to see what's changed, since quite a bit has since 2.0
Probably best to avoid updating to the 3.x branch for the time being.