I am not an expert, but I believe FTM version 16 (2006) will import the files form the previous versions ie those released in 1999. So that should not be a problem
However since FTM version 16 is now extinct I would do one of two things. If you do not plan to upgraded to FTM 2014, I would create FTM Books in Version 16, and stuff every fact into the file that the program is capable. If necessary make several books. I would then export them to PDF files. It is improbably that the PDF format will be come obsolete and unreadable in the next few decades, so you will always have the data available.
It you are thinking of upgrading, I would upgrade and import your dads files form the Version 16 FTM files.into FTM 2014.
I don't know what kind of computer you have, hopefully a pre Windows 8 system, as FTM Version 16 will not reliably run one the Windows 8 OS.
A note on FTM 2014. There is a lot of post in the forums about all of the difficulties people are having with it. Remember these are the people who post to the forum and they probably do not represent the average user of FTM 2014. Most seem to have very large files, one recent post was worried about the 4BG 32 bit file size limit. or are doing a lot of synchronized with Ancestry. While I do not have 2014, I upgraded from Version 16 to FTM 2012 and am still using it with no problems. I would highly recommend it for a new user.