If you are trying to convert older .br6 files from Bryce to the latest. br7 format, you will need to download the latest version of the program from internet (it is available for free now) and re-save it using the default program functions. There really is no other option how to perform this conversion, just keep in mind you will no longer be able to downgrade the version of your file, so always keep the original backup.
Convert Bryce version 6 scene to Bryce version 7 scene file.
We have found 2 software records in our database eligible for .br6 to .br7 file format conversion.
Microsoft Windows software - convert br6 to br7 on Windows
A graphics design tool for making 3D landscaping and animations
Convert from br6 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned br6 to br7. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert br6 to br7 on OS X
3D modeling and animation package for Mac.