Read the harddisk of a burned airport time machine

My external harddisk failed on my Imac. So I used the time machine to restore the lost volume. During this process my airport time capsule burned and stopped working. Time capsule can find the drive, but fails reading it. I took the HDD 6TB out and tried the old HDD 3TB, that was replaced 2 years ago, but working fine. Same negative result. I tried to read the drives in a wd elements external harddisk dock. I see only to volumes, APswap and APconfig. There seems to be another drive, that is invisible. This is on the 6TB hdd but also on the 3TB disk. So I conclude the drives is stil OK. Time machine on my mac does not recognise the drives. What do I need to to be able to read my time machine HDD ? Can I buy a small NAS from synology and install te drives? Or do I need data recovery ?