You would need to export your files from Business Pro. You can open and view this in Excel.
Once you have AccountRight you open a trial business and do an export from it to see the correct headers and layout. Then you can copy and paste your file information into the AccountRight export in Excel.
Once this is done, you can save that file and then you should be able to import it back into AccountRight. I had to do this with an old DOS based program and managed to import all the relevant files. You just need to practice in the trial business.