Hello, welcome to the site.
Actually, the model of your new Digital8 format Sony camcorder is DCR-TRV280. Small typo.
The old Hi8 camera shoots Hi8, and plays analog Video8 and Hi8 format 8mm Sony videotapes.
The new Digital8 camera shoots DV data on 8mm sized video tapes. It was a failed format by Sony, in attempts to buck the DV format (probably for licensing reasons?). But that was an uphill battle, and yet another foolish example of Sony not playing ball with the rest of the video world. Many of those cameras could easily be regarded as "beta" quality (as in beta testing, not Betamax) because the technology never really matured before it was dumped due to an inability to compete with regular DV cameras. A lot of them do not play analog Video8 or Hi8 formats, even though the tapes fit.
You really have two choices at this point:
(1) Send the tapes to a professional service, and get them captured to whatever digital format you'd like (DVD, Blu-ray, uncompressed files, etc)
(2) Buy a costly Hi8 video camera in known-good condition, which isn't as easy as it sounds. This is often more expensive than simply having the tapes professionally converted -- especially if you have less than 25 of them.
And yes, we do convert Video8 and Hi8 to digital formats, NTSC only (no PAL), as one of the services available at The Digital FAQ. Contact us
Hope that helps, and best wishes on your project.