If you go to Tools, Options in FTM 16 you will see a field Default Directory for new tree files. FTM 2012 will use this same directory if you take no action. This is how I would proceed.
Create a new folder for FTM 2010 files.
Copy your FTM 16 files to this folder.
When you install FTM 2012 point it to the FTM 2012 folder. It will convert your files in this folder but will leave your FTM 16 program and FTM 16 folder untouched. You can continue to use both FTM 16 and FTM 2012 until you are comfortable using FTM 2012. Just be sure you make all updates to the FTM 2012 file. Otherwise things can get out of sync and you may have to repeat the file conversion.
There is a considerable ;learning curve for FTM 2012 but I think you will find it worth it.