It's never been in the Market. You can get it here: http://www.droid-life.com/2010/06/17...otorola-droid/.
Simply download flash 10.1 from here, Adobe - Adobe Flash Player
Move the file to your sd card.
Open Astro file manager (free app), or whatever file manager you use for your droid.
Select the 10.1 file on your sd card, and install the application.
After install, go test to see if your flash is working via a flash video such as Salad Fingers 3: Nettles | Video Files