You'll have to talk to Gobbins as the Alliance CEO he is the only person who can accepts corps.
Seeing as you have such a low number of members though your chances might not be high.
Unless you have some real attachment to your corp name if might be easier to just join a corp already in Pandemic Horde.
Your best bet is to reach out to him via Discord at "Gobbins [HORDE]#0321"