I decided to replace the HDD of Mac mini to SSD because the HDD had trouble and it is difficult to fix the HDD.
I went to Akihabara to buy PX-256M5S but I bought PX-256M5P because a store staff to recommended it on the grounds that the saving rate PX-256M5P was higher and the price of PX-256M5P became close to one of PX-256M5S.
It took less than 30 minutes to replace.
The time of recovering from Time Machine is 1 hour and half. On the other hand, it took 3 hours to recover using with Firewire 800 HDD.
The issue is recovering "home" and "mail" from Backup3 because the backup data of TimeMachine is a half of year old.
The data loss is nothing but it is troublesome to restore the data to its original state.
I think to set TimeMichine to get backup once a month or a week.
My watch that I asked to maintain was back. The maintenance fee is about 2,2000 yen.
The maintenance is needed for 2 or 3 years and I decided 3 years interval for the maintenance.