You can't, unless you save the files from Moho 12 as Anime Studio 11 files. Otherwise, software would be forward-compatible, and you'd have to go back in time and kill your grandfather in order to get anything done! (At least, I *think* that's how it works...)
You can't have everything. Where would you put it?
The file format from 11 onwards is forward compatible. If the .moho has come from Version 12 then you can open it in AS11 but, ofc, none of the 12 features will be imported.
The 12 format is a zip file. Rename it to be xxxx.zip and extract and rename the .mohoproj file to be .animeproj
That will open in AS11 or you can put that back into a container and call the container a .anime
If the .moho came from version 5 or earlier it should open in 11 so there may be a file issue.
John, I may have a way for you save your granddad! If you time travel back to June 2016 ... viewtopic.php?f=5&t=29053&p=165851 (I'm not sure how many grandfathers needed to be sacrificed to create JSON tho')