Restore Mail post clean re-install

Hi from Paris, please excuse my rusty English...

Post clean Mojave re-install on a MBP, I got about everything covered, iTunes, Photos, Contacts (although few problems, but ok).

Now, the BIG thing remaining is "Mail". All of it.

I have 3 TM external drives, and I wanted ti do it the same way as the rest, manually.

Why ? In order to really restart on a "clean plate", real clean install, not re-importing old prefs / links / broken, corrupted, out of date... links and file and so on.

But here is the thing : I can not access the "library" files on the TM backups.

And I'am turning round and round and getting lost and mad...

Any advices please ?

Tanks of lot for any reply...

Marc