Or try this. Word Perfect help is as usual not all that helpful. It is possible that WP 10 no longer uses the .dat extension. Try to open the file in Word Perfect and copy it all. Try pasting that into an Excel sheet (or the Corel equivalent..I forget what it is). Then export it from there to ascii.
That now working, try downloading Windows converter packs (all) from MS and opening it in Excell and/or Access and/or Word. I suspect that one or the other would work. Again from there you export to Ascii and move on. You won't get object files, but then I don't think there are any in dat files.
If you do not have WP or if WP10 doesn't recognize the file, you can get a legacy copy for very little money. I would not hesitate to go for wp7 or 8 as oem. I suspect it wouldn't cost you more than $15 or so.