You need to find the installer and install Filemaker 11 on your new computer. If you cannot find one, you can probably get one if you can prove to FileMaker customer service that you had legally purchased copy in the first place.
If you cannot prove this, then you'll need to purchase a new copy of FileMaker so that you can install it on your new computer. FileMaker current sells FMP 12v2, but it can convert and open your older files to the new format. It is also probably still possible to make a "downgrade" purchase of FMP 11 and then no file conversion is needed.