Grab a copy of our ListStat tool, available either in the Pervasive ComponentZone, or from our web site at www.goldstarsoftware.com/tools.asp. ListStat allows you to do a pre-upgrade scan of files. I recommend the /2 option, which displays the File version, Page Size, and Record Count from each file in a comma-delimited format. To scan all subdirectories, add the /S option, and maybe the /W option. You command will probably look something like this:
LISTSTAT *.BTR /2 /sw
The 30-day trial should be plenty for a simple migration.
By the way -- if the files are 6.x format, then they are OK for use with PSQLv9 and PSQLv10 -- only Btrieve 5.x files will not work correctly. There are other reasons for rebuilding, of course, like performance, but 6.x files will still work.