Hi @Rocio-and-Mike0 ,
Here is a link that may help to achieve what you are looking to do:
https://www.airbnb.ca/help/article/1864
I did something similar in the past. I did create a new listing that included the two units that were listed separately, and linked the calendars so that if any of the listings were booked, the other listings could not be booked respectively. It was somewhat confusing, but I succeeded on my first try. I don't know if I could repeat the process again...
Hope that helps!