Did you try the master index for the topic of "teardown"?
Since you already eliminated one of the three 8th. generation models, how about telling us the actual model of the two possibilities remaining?
To find anything here, you really do need to use the appropriate, serial number based, model nicknames, see:
https://wiki.mobileread.com/wiki/Kindle_Serial_Numbers
In the case of 8th. gen devices, use the first six characters of the serial number.