I found on internet how activate the USB debugging mode of our tablet.
With a terminal emulator, that you can find on internet. Personally I used "Better Terminal Emulator Pro"
The command is
am start -a android.intent.action.MAIN -n com.android.settings/.DevelopmentSettings
The panel Debugging mode appear and you can switch on the usb debugging mode !
I used this method on my tab 450 it worked and normally it works for all tablets.
After that I tried all method to root the tablet:
"superoneclick" : http://shortfuse.org/
"z4root" : http://forum.xda-developers.com/showthread.php?t=833953 (last version 1.3.0)
but these methods are in reality for android 2.2
So for the tablet under froyo you can try !!??
On tablet 450 is android 2.3.3
So I tried
"gingerbreak" : http://forum.xda-developers.com/showthread.php?t=1044765
Unfortunatly it doesn t work
If someone have an idea!!
If someone can have the root, the next step is to install google apps with ROM manager and the zip of google apps that you can find here
but that is an other story ;-)