It's not entirely clear what your issue really is, nor what do you mean with "transfer".
As explained everywhere on this site, you only buy the airport, you don't buy an FS9 version or an FSX version, you are free to choose which version of the scenery you want to use. Even if you buy from FSX, you CAN activate the FS9 version, and vice-versa.
There's just one difference in how you activate the scenery, in case you want to run FSX or FS9 on the same computer and the same Windows installation, or not.
- If you are running FSX and FS9 on the same computer and the same Windows installation, then yes, you don't need to do anything: if you have activated a scenery in FSX, it will run as fully activated in FS9, and vice-versa.
- If you are running on different computers, or different Windows installs, then you need to manually activate the 2nd version, using the "Register Serial" function of the Addon Manager, using the Serial Number in your Email receipt.
Of course, you'll need to install the FS9 version under FS9 and the FSX version under FSX. The same scenery is NOT compatible with both sims! We have two different installers, one for FSX and one for FS9, you can't "move" your FSX scenery into FS9 and vice-versa.
Now, can you please describe exactly your problem ? Which scenery and which version have you installed, in which sim ? At the end of the installation, do you see the scenery, even if only in Trial, or not ?