Delphi 7, and indeed all released versions of Delphi Win32, only produce 32-bit executables. However, 32-bit executables work fine on 64-bit operating systems through the WOW64 emulator. Although this is an emulator, a word that usually means performance degradation, WOW64 performance is not always different from native 64-bit performance.
If you want to port a Delphi application to a 64-bit bit, you need to wait for the next version of Delphi, which will create 64-bit executables, to be released.
Then you will need to transfer the application from Delphi 7 to the latest version of Delphi. This will be a lot of work because you will also have to migrate from ANSI string code to Unicode string code. In my opinion, this part of the port will be more time consuming than the 32 - 64-bit part, and if you would like to get a start, it would be wise for you to start the Unicode port by upgrading it to Delphi XE.